@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/106391, title ="An Asymmetric Eclipse Seen Towards the Pre-Main Sequence Binary System V928 Tau", author = "van Dam, Dirk M. and Kenworthy, Matthew A.", journal = "arXiv", month = "October", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20201103-103003753", note = "We thank Dan Foreman-Mackey, Ian Czekala, Sarah Blunt for helpful discussions on\nthe astrometric modeling. This paper includes data collected by the Kepler mission\nand obtained from the MAST data archive at the Space Telescope Science Institute\n(STScI). Funding for the Kepler mission is provided by the NASA Science Mission\nDirectorate. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Part of this research was carried\nout at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004).\nTJD and EEM gratefully acknowledge support from the Jet Propulsion Laboratory Exoplanetary Science Initiative and NASA award 17-K2GO6-0030. Some of the data\npresented herein were obtained at the W. M. Keck Observatory from telescope time\nallocated to the National Aeronautics and Space Administration through the agency's\nscientific partnership with the California Institute of Technology and the University\nof California. The Observatory was made possible by the generous financial support\nof the W. M. Keck Foundation. The authors wish to recognize and acknowledge the\nvery significant cultural role and reverence that the summit of Maunakea has always\nhad within the indigenous Hawaiian community. We are most fortunate to have the\nopportunity to conduct observations from this mountain. This work has made use\nof data from the Asteroid Terrestrial-impact Last Alert System (ATLAS) project.\nATLAS is primarily funded to search for near earth asteroids through NASA grants\nNN12AR55G, 80NSSC18K0284, and 80NSSC18K1575; byproducts of the NEO search\ninclude images and catalogs from the survey area. The ATLAS science products have\nbeen made possible through the contributions of the University of Hawaii Institute\nfor Astronomy, the Queen's University Belfast, the Space Telescope Science Institute,\nand the South African Astronomical Observatory.\nSoftware: EVEREST (v2.0; Luger et al. (2016, 2018)), lightkurve (Lightkurve Collaboration et al. (2018)), exoplanet (Foreman-Mackey et al. (2020)), PyMC3 (Salvatier\net al. (2016)), Scipy (Virtanen et al. (2020), Matploltib (Hunter 2007), Astropy (Astropy Collaboration et al. 2013; Price-Whelan et al. 2018), Numpy (Oliphant 2006),\njktld (Southworth 2015)\n", revision_no = "12", abstract = "K2 observations of the weak-lined T Tauri binary V928 Tau A+B show the detection of a single, asymmetric eclipse which may be due to a previously unknown substellar companion eclipsing one component of the binary with an orbital period > 66 days. Over an interval of about 9 hours, one component of the binary dims by around 60%, returning to its normal brightness about 5 hours later. From modeling of the eclipse shape we find evidence that the eclipsing companion may be surrounded by a disk or a vast ring system. The modeled disk has a radius of 0.9923±0.0005R∗, with an inclination of 56.78±0.03∘, a tilt of 41.22±0.05∘, an impact parameter of −0.2506±0.0002R∗ and an opacity of 1.00. The occulting disk must also move at a transverse velocity of 6.637±0.002R∗day⁻¹, which depending on whether it orbits V928 Tau A or B, corresponds to approximately 73.53 or 69.26 kms⁻¹. A search in ground based archival data reveals additional dimming events, some of which suggest periodicity, but no unambiguous period associated with the eclipse observed by K2. We present a new epoch of astrometry which is used to further refine the orbit of the binary, presenting a new lower bound of 67 years, and constraints on the possible orbital periods of the eclipsing companion. The binary is also separated by 18\" (∼2250 au) from the lower mass CFHT-BD-Tau 7, which is likely associated with V928 Tau A+B. We also present new high dispersion optical spectroscopy that we use to characterize the unresolved stellar binary.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/106389, title ="An 8.8 minute orbital period eclipsing detached double white dwarf binary", author = "Burdge, Kevin B. and Coughlin, Michael W.", journal = "arXiv", month = "October", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20201103-093416233", note = "K.B.B thanks the National Aeronautics and Space\nAdministration and the Heising Simons Foundation for\nsupporting his research. M.W.C. acknowledges support\nfrom the National Science Foundation with grant number PHY-2010970. JF acknowledges support from an Innovator Grant from The Rose Hills Foundation, and the\nSloan Foundation through grant FG-2018-10515. TRM\nwas supported by the UK's Science and Technology Facilities Council through grant ST/T000406/1.\nBased on observations obtained with the Samuel\nOschin Telescope 48-inch and the 60-inch Telescope at\nthe Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National\nScience Foundation under Grant No. AST-1440341\nand a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center\nat Stockholm University, the University of Maryland,\nthe University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan,\nthe University of Wisconsin at Milwaukee, and Lawrence\nBerkeley National Laboratories. Operations are conducted by COO, IPAC, and UW.\nSome of the data presented herein were obtained at the\nW.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National\nAeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish\nto recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea\nhas always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to\nconduct observations from this mountain.\nFacilities: PO:1.2m (ZTF), Hale (CHIMERA),\nKeck:I (LRIS), Swift (XRT and UVOT)\nSoftware: Aplpy (Robitaille & Bressert 2012),\nAstropy (Astropy Collaboration et al. 2013), CU-VARBASE (https://github.com/johnh2o2/cuvarbase),\nLCURVE (Copperwheat et al. 2010), Lpipe (Perley\n2019), Multinest (Feroz et al. 2009), Numpy (van der\nWalt et al. 2011).\n", revision_no = "12", abstract = "We report the discovery of ZTF J2243+5242, an eclipsing double white dwarf binary with an orbital period of just 8.8 minutes, the second known eclipsing binary with an orbital period less than ten minutes. The system likely consists of two low-mass white dwarfs, and will merge in approximately 400,000 years to form either an isolated hot subdwarf or an R Coronae Borealis star. Like its 6.91min counterpart, ZTF J1539+5027, ZTF J2243+5242 will be among the strongest gravitational wave sources detectable by the space-based gravitational-wave detector The Laser Space Interferometer Antenna (LISA) because its gravitational-wave frequency falls near the peak of LISA's sensitivity. Based on its estimated distance of d = 2120⁺¹³¹₋₁₁₅pc, LISA should detect the source within its first few months of operation, and should achieve a signal-to-noise ratio of 87±5 after four years. We find component masses of M_A = 0.349^(+0.093)_(−0.074)M⊙ and M_B = 0.384^(+0.114)_(−0.074)M⊙, radii of R_A = 0.0308^(+0.0026)_(−0.0025)R⊙ and R_B = 0.0291^(+0.0032)_(−0.0024)R⊙, and effective temperatures of T_A = 22200⁺¹⁸⁰⁰₋₁₆₀₀K and T_B = 16200⁺¹²⁰⁰₋₁₀₀₀K. We determined all of these properties, and the distance to this system, using only photometric measurements, demonstrating a feasible way to estimate parameters for the large population of optically faint (r > 21m_(AB)) gravitational-wave sources which the Vera Rubin Observatory (VRO) and LISA should identify.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105981, title ="Periodic Eruptive Variability of the Isolated Pre-Main Sequence Star V347 Aurigae", author = "Dahm, S. E. and Hillenbrand, L. A.", journal = "arXiv", month = "October", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20201012-122808597", note = "We thank an anonymous referee for their helpful comments that improved this manuscript. SED is deeply indebted to G. H. Herbig who suggested that V347 Aur be\ntargeted for future observations. Herbig provided SED\nwith a short summary of his high dispersion spectra of\nV347 Aur obtained using HIRES on the Keck I telescope\nbetween 2003 and 2005.\nThis paper has made use of the Digitized Sky Surveys, which were produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166, the SIMBAD database operated at CDS, Strasbourg, France, and the 2MASS, a joint project of the\nUniversity of Massachusetts and the Infrared Processing and Analysis Center (IPAC)/California Institute of\nTechnology, funded by NASA and the National Science\nFoundation. This publication makes use of data products\nfrom the Wide-Field Infrared Survey Explorer, which is a\njoint project of the University of California, Los Angeles,\nand the Jet Propulsion Laboratory/California Institute\nof Technology, funded by the National Aeronautics and\nSpace Administration. Some of the data presented herein\nwere obtained at the W.M. Keck Observatory, which is\noperated as a scientific partnership among the California Institute of Technology, the University of California\nand the National Aeronautics and Space Administration.\nThe Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The\nPan-STARRS1 Surveys (PS1) and the PS1 public science\narchive have been made possible through contributions\nby the Institute for Astronomy, the University of Hawaii,\nthe Pan-STARRS Project Office, the Max-Planck Society\nand its participating institutes, the Max Planck Institute\nfor Astronomy, Heidelberg and the Max Planck Institute\nfor Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of\nEdinburgh, the Queen's University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres\nObservatory Global Telescope Network Incorporated, the\nNational Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and\nSpace Administration under Grant No. NNX08AR22G\nissued through the Planetary Science Division of the\nNASA Science Mission Directorate, the National Science\nFoundation Grant No. AST-1238877, the University of\nMaryland, Eotvos Lorand University (ELTE), the Los\nAlamos National Laboratory, and the Gordon and Betty\nMoore Foundation. ZTF is supported by the National\nScience Foundation and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University\nof Maryland, the University of Washington, Deutsches\nElektronen-Synchrotron and Humboldt University, Los\nAlamos National Laboratories, the TANGO Consortium\nof Taiwan, the University of Wisconsin at Milwaukee,\nand Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW.", revision_no = "12", abstract = "V347 Aurigae is associated with the small dark cloud L1438 and appears to be an isolated pre-main sequence star located at distance d≈200 pc. Multi-epoch, archival photometry reveals periodic brightness variations with amplitude V≈2.0 magnitudes occurring on timescales of ∼160 days that have persisted for decades. Regular cadence, optical imaging of the source with the Zwicky Transient Facility shows that a small reflection nebula illuminated by V347 Aur also fluctuates in brightness, at times fading completely. Multi-epoch, Keck/HIRES data suggests the presence of two distinct spectral components: a prominent emission-line dominated spectrum with a heavily veiled continuum correlated with the bright photometric state, and an M-type absorption line spectrum associated with quiescence. All spectra exhibit strong Balmer and He I line emission, consistent with accretion, as well as high velocity emission arising from the forbidden transitions of [O I], [N II], and [S II] that are generally associated with collimated jets and disk winds. There is no evidence in existing high dispersion spectroscopy or high resolution imaging for binarity of V347 Aur. The repeating outburst events are possibly linked to accretion instabilities induced by an undetected companion or a structure within the circumstellar disk that periodically increases the mass accretion rate. V347 Aur is perhaps analogous to an EXor-type variable, though more regularly recurring.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/106136, title ="Localized FRBs are Consistent with Magnetar Progenitors Formed in Core-Collapse Supernovae", author = "Bochenek, Christopher D. and Ravi, Vikram", journal = "arXiv", month = "September", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20201019-085557074", note = "This research was supported by the National Science Foundation under grant AST-1836018. \n\nSoftware: Astropy (Astropy Collaboration et al. 2018).", revision_no = "8", abstract = "With the localization of fast radio bursts (FRBs) to galaxies similar to the Milky Way and the detection of a bright radio burst from SGR J1935+2154 with energy comparable to extragalactic radio bursts, a magnetar origin for FRBs is evident. By studying the environments of FRBs, evidence for magnetar formation mechanisms not observed in the Milky Way may become apparent. In this paper, we use a sample of FRB host galaxies and a complete sample of core-collapse supernova (CCSN) hosts to determine whether FRB progenitors are consistent with a population of magnetars born in CCSNe. We also compare the FRB hosts to the hosts of hydrogen-poor superluminous supernovae (SLSNe-I) and long gamma-ray bursts (LGRBs) to determine whether the population of FRB hosts is compatible with a population of transients that may be connected to millisecond magnetars. After using a novel approach to scale the stellar masses and star-formation rates of each host galaxy to be statistically representative of z=0 galaxies, we find that the CCSN hosts and FRBs are consistent with arising from the same distribution. Furthermore, the FRB host distribution is inconsistent with the distribution of SLSNe-I and LGRB hosts. With the current sample of FRB host galaxies, our analysis shows that FRBs are consistent with a population of magnetars born through the collapse of giant, highly magnetic stars.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/106137, title ="Multiwavelength Radio Observations of Two Repeating Fast Radio Burst Sources: FRB 121102 and FRB 180916.J0158+65", author = "Pearlman, Aaron B. and Majid, Walid A.", journal = "arXiv", month = "September", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20201019-093428722", note = "We thank Professor Vicky Kaspi and the CHIME/FRB collaboration for their support of these observations and for providing the CHIME/FRB data used in Figure 3. \n\nA.B.P. acknowledges support by the Department of Defense (DoD) through the National Defense Science and Engineering Graduate (NDSEG) Fellowship Program and by the National Science Foundation (NSF) Graduate Research Fellowship under Grant No. DGE-1144469. J.W.T.H. acknowledges funding from an NWO Vici fellowship. \n\nWe thank the Jet Propulsion Laboratory’s Spontaneous Concept Research and Technology Development program for supporting this work. We also thank Dr. Stephen Lichten for providing programmatic support. In addition, we are grateful to the DSN scheduling team (Hernan Diaz, George Martinez, and Carleen Ward) and the GDSCC and MDSCC operations staff for scheduling and carrying out these observations. \n\nA portion of this research was performed at the Jet Propulsion Laboratory, California Institute of Technology and the Caltech campus, under a Research and Technology Development Grant through a contract with the National Aeronautics and Space Administration. U.S. government sponsorship is acknowledged.", revision_no = "10", abstract = "The spectra of fast radio bursts (FRBs) encode valuable information about the source's local environment, underlying emission mechanism(s), and the intervening media along the line of sight. We present results from a long-term multiwavelength radio monitoring campaign of two repeating FRB sources, FRB 121102 and FRB 180916.J0158+65, with the NASA Deep Space Network (DSN) 70-m radio telescopes (DSS-63 and DSS-14). The observations of FRB 121102 were performed simultaneously at 2.3 and 8.4 GHz, and spanned a total of 27.3 hr between 2019 September 19 and 2020 February 11. We detected 2 radio bursts in the 2.3 GHz frequency band from FRB 121102, but no evidence of radio emission was found at 8.4 GHz during any of our observations. We observed FRB 180916.J0158+65 simultaneously at 2.3 and 8.4 GHz, and also separately in the 1.5 GHz frequency band, for a total of 101.8 hr between 2019 September 19 and 2020 May 14. Our observations of FRB 180916.J0158+65 spanned multiple activity cycles during which the source was known to be active and covered a wide range of activity phases. Several of our observations occurred during times when bursts were detected from the source between 400-800 MHz with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) radio telescope. However, no radio bursts were detected from FRB~180916.J0158+65 at any of the frequencies used during our observations with the DSN radio telescopes. We find that FRB 180916.J0158+65's apparent activity is strongly frequency-dependent due to the narrowband nature of its radio bursts, which have less spectral occupancy at high radio frequencies (≳ 2 GHz). We also find that fewer or fainter bursts are emitted from the source at high radio frequencies. We discuss the implications of these results on possible progenitor models of repeating FRBs.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105947, title ="The First Extensive Spectroscopic Study of Young Stars in the North America and Pelican Nebulae Region", author = "Fang, Min and Hillenbrand, Lynne A.", journal = "arXiv", month = "September", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20201009-093746303", note = "Many thanks to the anonymous referee for comments that help to improve this paper. We thank Michael A. Kuhn for discussions about the NAP region. We recognize the contributions of former Caltech SURF students Daniel DeFelippis and Danika Wellington to our efforts. This paper uses data products produced by the OIR Telescope Data Center, supported by the Smithsonian Astrophysical Observatory. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. We use ZTF data, enabled by support from the NSF under grant AST-1440341, Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley national Laboratories. \n\nFacilities: Palomar:P200 (Norris), Keck:I (DEIMOS), MMT (Hectospec), Palomar:P48 (ZTF).", revision_no = "13", abstract = "We present a spectroscopic survey of over 3400 potential members in the North America and Pelican nebulae (NAP) using several low-resolution (R≈ 1300-2000) spectrographs: Palomar/Norris, WIYN/HYDRA, Keck/DEIMOS, and MMT/Hectospec. We identify 580 young stars as likely members of the NAP region based on criteria involving infrared excess, Li I 6708 absorption, X-ray emission, parallax, and proper motions. The spectral types of individual spectra are derived by fitting them with templates that are either empirical spectra of pre-main sequence stars, or model atmospheres. The templates are artificially veiled, and a best-fit combination of spectral type and veiling parameter is derived for each star. We use the spectral types with archival photometry to derive V-band extinction and stellar luminosity. From the H-R diagram, the median age of the young stars is about 1 Myr, with a luminosity dispersion of ∼0.3--0.4 dex. We investigate the photometric variability of the spectroscopic member sample using ZTF data, and conclude that photometric variability, while present, does not significantly contribute to the luminosity dispersion. While larger than the formal errors, the luminosity dispersion is smaller than if veiling were not taken into account in our spectral typing process. The measured ages of stellar kinematic groups, combined with inferred ages for embedded stellar populations revealed by Spitzer, suggests a sequential history of star formation in the NAP region.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105414, title ="Two Planets Straddling the Habitable Zone of The Nearby K dwarf Gl 414A", author = "Dedrick, Cayla M. and Fulton, Benjamin J.", journal = "arXiv", month = "September", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200916-112858438", note = "We are grateful to the time assignment committees of the California Institute of Technology, the University of California, the University of Hawaii, and NASA for their generous allocations of observing time. Without their long-term commitment to RV monitoring, these planets would likely remain unknown. We gratefully acknowledge the efforts and dedication of the staffs of the W. M. Keck Observatory and Mt. Hamilton. Research at theLick Observatory is partially supported by a generous gift from Google. We thank Geoff Marcy and Debra Fischer for their many nights of observing that contributed to the Keck data presented in this work, and R. Paul Butler and S. S. Vogt for many years of contributing to the data presented here. AWH acknowledges NSF grant AST-1517655. MRK acknowledges support from the NSF Graduate Research Fellowship, grant No. DGE 1339067. DJS was supported as an Eberly Research Fellow by the Eberly College of Science at the Pennsylvania State University. \n\nThe authors extend special thanks to those of Hawaiian ancestry on whose sacred mountain of Maunakea we are privileged to be guests. Without their generous hospitality, the Keck observations presented herein would not have been possible. \n\nThis work made use of the GNU Parallel package for large-scale multiprocessing (Tange 2018). This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This work made extensive use of the scipy (Virtanen et al. 2019), numpy (van der Walt et al. 2011), matplotlib (Hunter 2007), and pandas (McKinney 2010) Python packages. \n\nSimulations in this paper made use of the REBOUND code which is freely available at http://github.com/hannorein/rebound. \n\nFacility: Automated Planet Finder (Levy), Keck:I (HIRES), Exoplanet Archive", revision_no = "10", abstract = "We present the discovery of two planets orbiting the nearby (D = 11.9 pc) K7 dwarf Gl 414A. Gl 414A b is a sub-Neptune mass planet with M_b sin i_b = 9.28^(+3.19)_(−2.54) M_⊕ and a semi-major axis of 0.24 ± 0.01 au. Gl 414A c is a sub-Saturn mass planet with M_c sin i_c = 59.48^(+9.98)_(−9.69) M_⊕ and a semi-major axis of 1.43 ± 0.06 au. We jointly analyzed radial velocity data from Keck/HIRES and the Automated Planet Finder at Lick Observatory, as well as photometric data from KELT, to detect the two planets as well as two additional signals related to the rotationally-modulated activity and the long term magnetic activity cycle of the star. The outer planet in this system is a potential candidate for future direct imaging missions.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105427, title ="A kilometer-scale asteroid inside Venus's orbit", author = "Ip, W.-H. and Bolin, B.", journal = "arXiv", month = "September", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200916-112945883", note = "Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. \n\nSED Machine is based upon work supported by the National Science Foundation under Grant No. 1106171 \n\nThe KPED team thanks the National Science Foundation and the National Optical Astronomical Observatory for making the Kitt Peak 2.1-m telescope available. We thank the observatory staff at Kitt Peak for their efforts to assist Robo-AO KP operations. The KPED team thanks the National Science Foundation, the National Optical Astronomical Observatory, the Caltech Space Innovation Council and the Murty family for support in the building and operation of\nKPED. In addition, they thank the CHIMERA project for use of the Electron Multiplying CCD (EMCCD). \n\nThe authors would like to thank Alessandro Morbidelli for useful discussion in the interpretation of the first inner-Venus asteroid discovery as well as providing the synthetic asteroid population used to model our survey efficiencies. \n\nM. W. Coughlin acknowledges support from the National Science Foundation with grant number PHY-2010970. \n\nC.F. gratefully acknowledges the support of his research by the Heising-Simons Foundation (#2018-0907). \n\nSome of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. \n\nThe authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. \n\nThis work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. \n\nAuthors Contributions. W.-H.I. helped initiate, design and secure P48 time for the ZTF Twilight. B.T.B. discovered 2020 AV₂ in the ZTF data and realized it had an orbit interior to Venus’, led the study, wrote the manuscript, reviewed and scanned all candidate asteroid detections for the duration of this study, helped design and secure time for the Twilight survey and for follow-up, prepared and executed follow-up observations, reduced the photometric and spectroscopic data, did the astrometry, orbit determination, helped generate the synthetic NEA population, calculated the survey completeness and estimates of the inner-Venus asteroid population. F.J.M. served as the Science Data System Lead of the ZTF collaboration, wrote and maintained software for extraction of moving objects in ZTF data, calculated the survey completeness, maintained the ZTF data system, helped secure P48 time for the ZTF Twilight survey, helped design and initiate the Twilight survey. Q.Y. contributed code used to schedule the ZTF survey and contributed improvements to the moving object identification pipeline, and helped initiate and design the Twilight survey. E.K. monitored the NEA discovery performance of the ZTF survey. G.H. helped with the interpretation of the completeness calculation, helped prepare the manuscript, served as the Primary Investigator of the team observing NEAs with ZTF and as the Data Archive Director of the ZTF collaboration, helped design the cadence, secure P48 time for the ZTF Twilight survey and is one of its initiators. E.K. monitored the NEA discovery performance of the ZTF survey. G.H. served as the Primary Investigator of the team observing NEAs with ZTF and as the Data Archive Director of the ZTF collaboration, helped design the cadence, secure P48 time for the ZTF Twilight survey and is one of its initiators. E.K. monitored the NEA discovery performance of the ZTF survey. G.H. served as the Primary Investigator of the team observing NEAs with ZTF and as the Data Archive Director of the ZTF collaboration, helped design the cadence, secure P48 time for the ZTF Twilight survey and is one of its initiators. T.A. and M.C. performed follow-up observations of 2020 AV₂ with KPED and contributed to the reduction of photometry. M.G. served as the Project Scientist of ZTF, secured time with Keck I and took spectroscopic observations of 2020 AV₂ with Keck I/LRIS and reduced spectral data. R.W. performed follow-up observations of 2020 AV₂ with SEDM. K.P.D. contributed to planning follow-up observations of 2020 AV₂. C.F. contributed to the planning of spectroscopy observations of 2020 AV₂ with Keck and spectroscopic data reduction. Z.-Y.L. contributed to the interpretation of the 2020 AV₂ spectroscopy data. J.W.M. contributed to follow-up observations of 2020 AV₂. J.P. and R.Q. contributed to the reduction of photometry and follow-up observations of 2020 AV₂. C.-K.C., C.-C.N. and H.T. contributed to securing time with the P48 for ZTF Solar System observations. C.Z., C.M.C and J.S. were members of the team that conducts follow-up observations of ZTF Solar System discoveries. P.D. and L.A.M. helped secure time for follow-up observations of 2020 AV₂. M.G. helped generate the synthetic NEA population. K.B.B. and K.D. contributed to the reduction of Keck/LRIS spectroscopy data of 2020 AV₂. E.C.B. served as the Survey Scientist of the ZTF collaboration and scheduled the observations taken with the P48 during the ZTF Twilight survey. S.B.C. contributed to the planning of P48 time used in the Twilight survey. D.A.D, A.M. and P.J.M. wrote and maintained software and machine learning algorithms for the ZTF data pipeline and identification of sources in ZTF data. A.M. served as the Machine Learning Lead for the ZTF collaboration. R.D. served as the Project Manager of the ZTF collaboration and contributed to the design and construction of the ZTF camera. D.H. contributed to the design and construction of the ZTF camera. M.K. served as the Primary Investigator of the Global Relay of Observatories Watching Transients Happen (GROWTH) team for follow-up of ZTF discoveries. S.R.K. served as the Principal Investigator of the ZTF collaboration and survey. T.K. and M.T.S. contributed to the ZTF calibration pipeline. J.D.N. contributed to SEDM operations and observations of 2020 AV₂. R.R. contributed to maintaining ZTF operations. H.R. contributed to SEDM operations. E.S. contributed to KPED operations and observations of 2020 AV₂. R.M.S. served as the Lead Camera Engineer for the ZTF survey and lead the design and construction of the ZTF camera. J.S. contributed to SEDM operations and observations of 2020 AV₂. L.Y. contributed to planning and securing of telescope time for follow-up observations of 2020 AV₂.", revision_no = "11", abstract = "Near-Earth asteroid population models predict the existence of asteroids located inside the orbit of Venus. However, despite searches up to the end of 2019, none have been found. Here we report the discovery by the Zwicky Transient Facility of the first known asteroid located inside of Venus' orbit, 2020 AV₂, possessing an aphelion distance of 0.65 au and ∼2 km in size. While it is possible that 2020 AV₂ is the largest of its kind, we find that its discovery is surprising in the context of population models where the expected count is close to zero. If this discovery is not a statistical fluke, then 2020 AV₂ may come from a yet undiscovered source population of asteroids interior to Venus, and currently favored asteroid population models may need to be adjusted.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105416, title ="Physical Parameters of the Multi-Planet Systems HD 106315 and GJ 9827", author = "Kosiarek, Molly R. and Berardo, David A.", journal = "arXiv", month = "September", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200916-112905779", note = "M.R.K is supported by the NSF Graduate Research Fellowship, grant No. DGE 1339067. \n\nThe authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. \n\nSome of the observations in the paper made use of the High-Resolution Imaging instrument Zorro. Zorro was funded by the NASA Exoplanet Exploration Program and built at the NASA Ames Research Center by Steve B. Howell, Nic Scott, Elliott P. Horch, and Emmett Quigley. Zorro is mounted on the Gemini South telescope of the international Gemini Observatory, a program of NSFs OIR Lab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. \n\nThis work is based in part on observations made with the Spitzer Space Telescope, which was operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. \n\nThis research has made use of the Exoplanet Followup Observing Program (ExoFOP), which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration. \n\nPart of the research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). \n\nThis work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. \n\nJMAM gratefully acknowledges support from the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1842400. JMAM also thanks the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining Grant No. 1829740, the Brinson Foundation, and the Moore Foundation; his participation in the program has benefited this work. \n\nP.D. acknowledges support from a National Science Foundation Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1903811. \n\nL.M.W. is supported by the Beatrice Watson Parrent Fellowship and NASA ADAP Grant 80NSSC19K0597. \n\nFacilities: Keck:I(HIRES), Magellan:Clay(PFS), Spitzer, APF, TSU:AIT, Gemini:South(Zorro) \n\nSoftware: radvel (Fulton et al. 2018), batman (Kreidberg 2015), SpecMatch-Emp (Yee et al. 2017), isoclassify (Huber et al. 2017), spock (Tamayo et al. 2020), rebound (Rein & Liu 2011)", revision_no = "20", abstract = "HD 106315 and GJ 9827 are two bright, nearby stars that host multiple super-Earths and sub-Neptunes discovered by K2 that are well suited for atmospheric characterization. We refined the planets' ephemerides through Spitzer transits, enabling accurate transit prediction required for future atmospheric characterization through transmission spectroscopy. Through a multi-year high-cadence observing campaign with Keck/HIRES and Magellan/PFS, we improved the planets' mass measurements in anticipation of HST transmission spectroscopy. For GJ 9827, we modeled activity-induced radial velocity signals with a Gaussian process informed from the Calcium II H&K lines in order to more accurately model the effect of stellar noise on our data. We found planet masses of M_b = 4.87 ± 0.37 M_⊕, M_c = 1.92 ± 0.49 M_⊕, and M_d = 3.42 ± 0.62 M_⊕. For HD 106315, we found that such activity-radial velocity decorrelation was not effective due to the reduced presence of spots and speculate that this may extend to other hot stars as well (T_(eff) > 6200 K). We found planet masses of M_b = 10.5 ± 3.1 M_⊕ and M_c = 12.0 ± 3.8 M_⊕. We investigated all of the planets' compositions through comparing their masses and radii to a range of interior models. GJ 9827 b and GJ 9827 c are both consistent with an Earth-like rocky composition, GJ 9827 d and HD 106315 b both require additional volatiles and are consistent with moderate amounts of water or hydrogen/helium, and HD 106315 c is consistent with 10% hydrogen/helium by mass.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105415, title ="The TESS-Keck Survey II: Masses of Three Sub-Neptunes Transiting the Galactic Thick-Disk Star TOI-561", author = "Weiss, Lauren M. and Dai, Fei", journal = "arXiv", month = "September", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200916-112902099", note = "We thank the time assignment committees of the University of California, the California Institute of Technology, NASA, and the University of Hawaii for supporting the TESS-Keck Survey with observing time at Keck Observatory and on the Automated Planet Finder. \n\nWe thank NASA for funding associated with our Key Strategic Mission Support project. We gratefully acknowledge the efforts and dedication of the Keck Observatory staff for support of HIRES and remote observing. We recognize and acknowledge the cultural role and reverence that the summit of Maunakea has within the indigenous Hawaiian community. We are deeply grateful to have the opportunity to conduct observations from this mountain. \n\nWe thank Ken and Gloria Levy, who supported the construction of the Levy Spectrometer on the Automated Planet Finder. We thank the University of California and Google for supporting Lick Observatory and the UCO staff for their dedicated work scheduling and operating the telescopes of Lick Observatory. This paper is based on data collected by the TESS mission. Funding for the TESS mission is provided by the NASA Explorer Program. We acknowledge the use of public TESS Alert data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. We thank David Latham for organizing the TESS community follow-up program, which brought together the widespread authorship and diversity of resources presented in this manuscript. \n\nObservations in the paper made use of the High-Resolution Imaging instrument ‘Alopeke. ‘Alopeke was funded by the NASA Exoplanet Exploration Program and built at the NASA Ames Research Center by Steve B. Howell, Nic Scott, Elliott P. Horch, and Emmett Quigley. ‘Alopeke was mounted on the Gemini North telescope of the international Gemini Observatory, a program of NSF’s OIR Lab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). \n\nThis work makes use of observations from the LCOGT network. This article is based on observations made with the MuSCAT2 instrument, developed by ABC, at Telescopio Carlos Sánchez operated on the island of Tenerife by the IAC in the Spanish Observatorio del Teide. This work is partly supported by JSPS KAKENHI Grant Numbers JP17H04574, JP18H01265 and JP18H05439, and JST PRESTO Grant Number JPMJPR1775. \n\nThis research has made use of the Exoplanet Followup Observing Program (ExoFOP), which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration. Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. \n\nL.M.W. is supported by the Beatrice Watson Parrent Fellowship and NASA ADAP Grant 80NSSC19K0597. D.H. acknowledges support from the Alfred P. Sloan Foundation, the National Aeronautics and Space Administration (80NSSC18K1585, 80NSSC19K0379), and the National Science Foundation (AST-1717000). E.A.P. acknowledges the support of the Alfred P. Sloan Foundation. C.D.D. acknowledges the support of the Hellman Family Faculty Fund, the Alfred P. Sloan Foundation, the David & Lucile Packard Foundation, and the National Aeronautics and Space Administration via the TESS Guest Investigator Program (80NSSC18K1583). I.J.M.C. acknowledges support from the NSF through grant AST-1824644. Z.R.C. acknowledges support from the TESS Guest Investigator Program (80NSSC18K18584). A.C. acknowledges support from the National Science Foundation through the Graduate Research Fellowship Program (DGE 1842402). P.D. acknowledges support from a National Science Foundation Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1903811. A.B. is supported by the NSF Graduate Research Fellowship, grant No. DGE 1745301. R.A.R. is supported by the NSF Graduate Research Fellowship, grant No. DGE 1745301. M.R.K. is supported by the NSF Graduate Research Fellowship, grant No. DGE 1339067. J.N.W. thanks the Heising Simons Foundation for support. \n\nFacilities: TESS, KeckI-HIRES, Gemini-North-NIRI, Gemini-South-Zorro, Palomar, SOAR, LCOGT, El Sauce, PEST, MuSCAT2 \n\nSoftware: Python, Astropy, radvel, emcee, Spectra Made Easy, Specmatch, isoclassify, AstroImageJ, lightkurve, spock, kiaukoku", revision_no = "14", abstract = "We report the discovery of TOI-561, a multiplanet system containing an ultra-short period planet (USP), based on photometry from the NASA TESS Mission and ground-based follow-up. This bright (V = 10.2) star hosts three small transiting planets: TOI-561 b (TOI-561.02, P = 0.44 days, R_b = 1.45 ± 0.11 R_⊕), c (TOI-561.01, P = 10.8 days, R_c = 2.90 ± 0.13 R_⊕), and d (TOI-561.03, P = 16.4 days, R_d = 2.32 ± 0.16 R_⊕). The star is chemically ([Fe/H] = -0.41, [α/Fe] = +0.23) and kinematically consistent with the galactic thick disk population, making TOI-561 one of the oldest (10 ± 3 Gyr) and most metal-poor planetary systems discovered yet. We confirm the planetary nature of the candidates with high-contrast imaging, ground-based photometric follow-up and radial velocities from Keck/HIRES. Planet b has a mass and density of 3.2 ± 0.8 M_⊕ and 5.6^(+2.2)_(-1.7) g cm⁻³, consistent with a rocky composition. Its lower-than-average density is consistent with an iron-poor composition, although an Earth-like iron-to-silicates ratio is not ruled out. Planet c is 6.5±2.4M⊕ and 1.45 ± 0.55 g cm⁻³, and planet d is 2.4^(+2.3)_(-1.7) M_⊕ and 1.1^(+1.1)_(-0.7) g cm⁻³, both of which are consistent with an interior rocky core overlaid with a low-mass volatile envelope. TOI-561 b is the first rocky world around a galactic thick-disk star confirmed with radial velocities and one of the best rocky planets for thermal emission studies.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105433, title ="A systematic search of Zwicky Transient Facility data for ultracompact binary LISA-detectable gravitational-wave sources", author = "Burdge, Kevin B. and Prince, Thomas A.", journal = "arXiv", month = "September", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200916-113006965", note = "K.B.B thanks the National Aeronautics and Space Administration and the Heising Simons Foundation for supporting his research. \n\nM. W. C. acknowledges support from the National Science Foundation with grant number PHY-2010970. \n\nP.R-G acknowledges support from the State Research Agency (AEI) of the Spanish Ministry of Science, Innovation and Universities (MCIU), and the European Regional Development Fund (FEDER) under grant AYA2017-83383-P. \n\nV.S.D, ULTRACAM and HiPERCAM are supported by STFC. \n\nThe research leading to these results has received funding from the European Research Council under the European Union's Horizon 2020 research and innovation programme numbers 677706 (WD3D) and 340040 (HiPERCAM). \n\nBased on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. \n\nBased on observations made with the Gran Telescopio Canarias (GTC) installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, in the island of La Palma. \n\nBased on observations made at the European Southern Observatory New Technology Telescope (NTT), La Silla. \n\nThe KPED team thanks the National Science Foundation and the National Optical Astronomical Observatory for making the Kitt Peak 2.1-m telescope available. The KPED team thanks the National Science Foundation, the National Optical Astronomical Observatory and the Murty family for support in the building and operation of KPED. In addition, they thank the CHIMERA project for use of the Electron Multiplying CCD (EM-CCD). \n\nSome of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. \n\nThis article is based on observations made in the Observatorios de Canarias del IAC with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group of Telescopes in the Observatorio del Roque de los Muchachos. This research benefited from interactions at the ZTF Theory Network Meeting that were funded by the Gordon and Betty Moore Foundation through Grant GBMF5076 and support from the National Science Foundation through PHY-1748958. \n\nFacilities: PO:1.2m (ZTF), KPNO:2.1m (KPED), NTT (ULTRACAM), Hale (CHIMERA, DBSP), GTC (HiPERCAM), Keck:I (LRIS)", revision_no = "15", abstract = "Using photometry collected with the Zwicky Transient Facility (ZTF), we are conducting an ongoing survey for binary systems with short orbital periods (P_b < 1 hr) with the goal of identifying new gravitational-wave sources detectable by the upcoming Laser Interferometer Space Antenna (LISA). Here, we present a sample of fifteen binary systems discovered thus far, with orbital periods ranging from 6.91 min to 56.35 min. Of the fifteen systems, seven are eclipsing systems which do not show signs of significant mass transfer. Additionally, we have discovered two AM Canum Venaticorum (AM CVn) systems and six systems exhibiting primarily ellipsoidal variations in their light curves. We present follow-up spectroscopy and high-speed photometry confirming the nature of these systems, estimates of their LISA signal-to-noise ratios (SNR), and a discussion of their physical characteristics.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105412, title ="The peculiar Ca-rich SN 2019ehk: Evidence for a Type IIb core-collapse supernova from a low mass stripped progenitor", author = "De, Kishalay and Fremling, U. Christoffer", journal = "arXiv", month = "September", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200916-112851135", note = "We thank W. Jacobson-Galan for providing the spectral sequence of SN 2019ehk. We thank J. Sollerman for constructive comments on this manuscript. We thank L. Bildsten and A. Polin for valuable discussions. We thank D. Perley for assistance with lpipe. \n\nThis work was supported by the GROWTH (Global Relay of Observatories Watching Transients Happen) project funded by the National Science Foundation under PIRE Grant No 1545949. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. AGYs research is supported by the EU via ERC grant No. 725161, the ISF GW excellence center, an IMOS space infrastructure grant and BSF/Transformative and GIF grants, as well as The Benoziyo Endowment Fund for the Advancement of Science, the Deloro Institute for Advanced Research in Space and Optics, The Veronika A. Rabl Physics Discretionary Fund, Paul and Tina Gardner, Yeda-Sela and the WIS-CIT joint research grant; AGY is the recipient of the Helen and Martin Kimmel Award for Innovative Investigation.", revision_no = "11", abstract = "The nature of the peculiar 'Ca-rich' SN 2019ehk in the nearby galaxy M100 remains unclear. Its origin has been debated as either a stripped core-collapse supernova or a thermonuclear helium detonation event. Here, we present very late-time photometry of the transient obtained with the Keck I telescope at ≈280 days from peak light. Using the photometry to perform accurate flux calibration of a contemporaneous nebular phase spectrum, we measure an [O I] luminosity of (0.23−0.78) × 10³⁸ erg s⁻¹ and [Ca II] luminosity of (3.4−9.1) × 10³⁸ erg s⁻¹ over the range of the uncertain extinction along the line of sight. We use these measurements to derive lower limits on the synthesized oxygen mass of ≈0.005−0.05 M_⊙. The oxygen mass is a sensitive tracer of the progenitor mass for core-collapse supernovae, and our estimate is consistent with explosions of very low mass CO cores of 1.45−1.5 M_⊙, corresponding to He core masses of ≈1.8−2.0 M_⊙. We present high quality peak light optical spectra of the transient and highlight features of hydrogen in both the early ('flash') and photospheric phase spectra, that suggest the presence of ≳0.02 M_⊙ of hydrogen in the progenitor at the time of explosion. The presence of H, together with the large [Ca II]/[O I] ratio (≈10−15) in the nebular phase is consistent with SN 2019ehk being a Type IIb core-collapse supernova from a stripped low mass (≈9−9.5 M_⊙) progenitor, similar to the Ca-rich SN IIb iPTF 15eqv. These results provide evidence for a likely class of 'Ca-rich' core-collapse supernovae from stripped low mass progenitors in star forming environments, distinct from the thermonuclear Ca-rich gap transients in old environments.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105470, title ="The mass budget for intermediate-mass black holes in dense star clusters", author = "Shi, Yanlong and Grudić, Michael Y.", journal = "arXiv", month = "August", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200922-124141959", note = "Support for YS & PFH was provided by NSF Collaborative Research Grants 1715847 & 1911233, NSF CAREER grant 1455342, NASA grants 80NSSC18K0562, JPL 1589742. Numerical calculations were run on the Caltech compute cluster “Wheeler,” allocations FTA-Hopkins supported by the NSF and TACC, and NASA HEC SMD-16-7592.", revision_no = "10", abstract = "Intermediate-mass black holes (IMBHs) could form via runaway merging of massive stars in a young massive star cluster (YMC). We combine a suite of numerical simulations of YMC formation with a semi-analytic model for dynamical friction and merging of massive stars and evolution of a central quasi-star, to predict how final quasi-star and relic IMBH masses scale with cluster properties (and compare with observations). The simulations argue that inner YMC density profiles at formation are steep (approaching isothermal), producing some efficient merging even in clusters with relatively low effective densities, unlike models which assume flat central profiles resembling those of globular clusters (GCs) after central relaxation. Our results can be approximated by simple analytic scalings, with M_(IMBH) ∝ v^(3/2)_(cl) where v²_(cl) = GM_(cl)/r_h is the circular velocity in terms of initial cluster mass M_(cl) and half-mass radius rh. While this suggests IMBH formation is possible even in typical clusters, we show that predicted IMBH masses for these systems are small, ∼100−1000 M_⊙ or ∼0.0003M_(cl), below even the most conservative observational upper limits in all known cases. The IMBH mass could reach ≳ 10⁴ M⊙ in the centers nuclear star clusters, ultra-compact dwarfs, or compact ellipticals, but in all these cases the prediction remains far below the present observed supermassive BH masses in these systems.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105424, title ="A large fraction of hydrogen-rich supernova progenitors experience elevated mass loss shortly prior to explosion", author = "Bruch, Rachel J. and Gal-Yam, Avishay", journal = "arXiv", month = "August", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200916-112934888", note = "AGY's research is supported by the EU via ERC grant No. 725161, the ISF GW excellence center, an IMOS space infrastructure grant and BSF/Transformative and GIF grants, as well as The Benoziyo Endowment Fund for the Advancement of Science, the Deloro Institute for Advanced Research in Space and Optics, The Veronika A. Rabl Physics Discretionary Fund, Paul and Tina Gardner, Yeda-Sela and the WIS-CIT joint research grant; AGY is the recipient of the Helen and Martin Kimmel Award for Innovative Investigation. The ztfquery code was funded by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 759194 - USNAC, PI: Rigault). The ZTF forced-photometry service was funded under the Heising-Simons Foundation grant #12540303 (PI: Graham). Based on observations obtained with the Samuel Oschin 48-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. The data presented here were obtained [in part] with ALFOSC, which is provided by the Instituto de Astrofisica de Andalucia (IAA) under a joint agreement with the University of Copenhagen and NOTSA. A.A.M. is funded by the LSST Corporation, the Brinson Foundation, and the Moore Foundation in support of the LSSTC Data Science Fellowship Program; he also receives support as a CIERA Fellow by the CIERA Postdoctoral Fellowship Program (Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University).", revision_no = "14", abstract = "Spectroscopic detection of narrow emission lines traces the presence of circumstellar mass distributions around massive stars exploding as core-collapse supernovae. Transient emission lines disappearing shortly after the supernova explosion suggest that the spatial extent of such material is compact, and hence imply an increased mass loss shortly prior to explosion. Here, we present a systematic survey for such transient emission lines (Flash Spectroscopy) among Type II supernovae detected in the first year of the Zwicky Transient Facility (ZTF) survey. We find that at least six out of ten events for which a spectrum was obtained within two days of estimated explosion time show evidence for such transient flash lines. Our measured flash event fraction (>30% at 95% confidence level) indicates that elevated mass loss is a common process occurring in massive stars that are about to explode as supernovae.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105263, title ="Revisiting the Gas Kinematics in SSA22 Lyman-α Blob 1 with Radiative Transfer Modeling in a Multiphase, Clumpy Medium", author = "Li, Zhihui and Steidel, Charles C.", journal = "arXiv", month = "August", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200908-075612693", note = "ZL acknowledges Michael Zhang, for his professional guidance and kind company during the excruciating debugging process. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. We are also grateful to the dedicated staff of the W.M. Keck Observatory who keep the instruments and telescopes running effectively. MG was supported by NASA through the NASA Hubble Fellowship grant HST-HF2-51409 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. Numerical calculations were run on the Caltech compute cluster “Wheeler,” allocations from XSEDE TG-AST130039 and PRAC NSF.1713353 supported by the NSF, and NASA HEC SMD-16-7592. This research made use of Montage. It is funded by the National Science Foundation under Grant Number ACI-1440620, and was previously funded by the National Aeronautics and Space Administration’s Earth Science Technology Office, Computation Technologies Project, under Cooperative Agreement Number NCC5-626 between NASA and the California Institute of Technology.", revision_no = "12", abstract = "We present new observations of Lyman-α (Lyα) Blob 1 (LAB1) in the SSA22 protocluster region (z = 3.09) using the Keck Cosmic Web Imager (KCWI) and the Keck Multi-object Spectrometer for Infrared Exploration (MOSFIRE). By applying matched filtering to the KCWI datacube, we have created a narrow-band Lyα image and identified several prominent features. By comparing the spatial distributions and intensities of Lyα and Hβ, we find that recombination of photo-ionized HI gas followed by resonant scattering is sufficient to explain all the observed Lyα/Hβ ratios. We further decode the spatially-resolved Lyα profiles using both moment maps and Monte-Carlo radiative transfer (MCRT) modeling. By fitting a set of multiphase, 'clumpy' models to the observed Lyα profiles, we are able to reasonably constrain many parameters, namely the HI number density in the inter-clump medium (ICM), the cloud volume filling factor, the random velocity and outflow velocity of the clumps, the HI outflow velocity of the ICM and the local systemic redshift. Our model has successfully reproduced the diverse Lyα morphologies at different locations, and the main results are: (1) The observed Lyα spectra require relatively few clumps per line-of-sight as they have significant fluxes at the line center; (2) The velocity dispersion of the clumps yields a significant broadening of the spectra as observed; (3) The clump bulk outflow can also cause additional broadening if the HI in the ICM is optically thick; (4) The HI in the ICM is responsible for the absorption feature close to the Lyα line center.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/104982, title ="Paving the Way to Future Missions: the Roman Space Telescope Coronagraph Technology Demonstration", author = "Mennesson, B. and Juanola-Parramon, R.", journal = "arXiv", month = "August", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200817-125215162", note = "Part of the research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. © 2020 California Institute of Technology. Government sponsorship acknowledged.", revision_no = "10", abstract = "This document summarizes how far the Nancy Grace Roman Space Telescope Coronagraph Instrument (Roman CGI) will go toward demonstrating high-contrast imaging and spectroscopic requirements for potential future exoplanet direct imaging missions, illustrated by the HabEx and LUVOIR concepts. The assessment is made for two levels of assumed CGI performance: (i) current best estimate (CBE) as of August 2020, based on laboratory results and realistic end-to-end simulations with JPL-standard Model Uncertainty Factors (MUFs); (ii) CGI design specifications inherited from Phase B requirements. We find that the predicted performance (CBE) of many CGI subsystems compares favorably with the needs of future missions, despite providing more modest point source detection limits than future missions. This is essentially due to the challenging pupil of the Roman Space Telescope; this pupil pushes the coronagraph masks sensitivities to misalignments to be commensurate with future missions. In particular, CGI will demonstrate active low-order wavefront control and photon counting capabilities at levels of performance either higher than, or comparable to, the needs of future missions.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105411, title ="The Palomar Transient Factory Core-Collapse Supernova Host-Galaxy Sample. I. Host-Galaxy Distribution Functions and Environment-Dependence of CCSNe", author = "Schulze, Steve and Yaron, Ofer", journal = "arXiv", month = "August", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200916-112847454", note = "We thank Nino Cucchiara, Thomas de Jaeger, Harald Ebeling, David Levitan, Bruce Margon, Jon Mauerhan, Jacob Rex, David Sand, Jeffrey M. Silverman, Vicky Toy, and Brad Tucker for performing some of the observations and Ido Irani and Maryam Modjaz for valuable discussions. \n\nI. Arcavi is a CIFAR Azrieli Global Scholar in the Gravity and the Extreme Universe Program and acknowledges support from that program, from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement number 852097), from the Israel Science Foundation (grant numbers 2108/18 and 2752/19), from the United States - Israel Binational Science Foundation (BSF), and from the Israeli Council for Higher Education Alon Fellowship. J. S. Bloom was partially supported by a Gordon and Betty Moore Foundation Data-Driven Discovery grant. The UCSC team is supported in part by NASA grant NNG17PX03C, the Gordon & Betty Moore Foundation, the Heising-Simons Foundation, and by a fellowship from the David and Lucile Packard Foundation to R. J. Foley. A. V. Filippenko acknowledges support from the U.S. National Science Foundation, the Christopher R. Redlich Fund, the TABASGO Foundation, and the Miller Institute for Basic Research in Science (U.C. Berkeley). M. Fraser is supported by a Royal Society - Science Foundation Ireland University Research Fellowship. A. GalYam’s research is supported by the EU via ERC grant 725161, the ISF GW excellence center, an IMOS space infrastructure grant and BSF/Transformative and GIF grants, as well as The Benoziyo Endowment Fund for the Advancement of Science, the Deloro Institute for Advanced Research in Space and Optics, The Veronika A. Rabl Physics Discretionary Fund, Paul and Tina Gardner, Yeda-Sela and the WIS-CIT joint research grant; A. Gal-Yam is the recipient of the Helen and Martin Kimmel Award for Innovative Investigation. A. Y. Q. Ho was supported by a National Science Foundation Graduate Research Fellowship under grant DGE-1144469, and by the GROWTH project funded by the National Science Foundation under PIRE grant 1545949. D. A. Howell, G. Hosseinzadeh, and C. McCully were supported by NSF grant AST-1313484. M. M. Kasliwal acknowledges support by the GROWTH (Global Relay of Observatories Watching Transients Happen) project funded by the National Science Foundation under PIRE Grant No 1545949. S. Knežević was supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia through contract 451-03-68/2020/14/20002 made with the Astronomical Observatory of Belgrade. G. Leloudas is supported by a research grant (19054) from VILLUM FONDEN. R. Lunnan is supported by a Marie Skłodowska-Curie Individual Fellowship within the Horizon 2020 European Union (EU) Framework Programme for Research and Innovation (H2020-MSCA-IF-2017-794467). K. Maguire acknowledges funding from EU H2020 ERC grant 758638 T. Petrushevska acknowledges the financial support from the Slovenian Research Agency (grants I0-0033,\nP1-0031, J1-8136 and Z1-1853). S. Schulze gratefully acknowledges support provided by the Feinberg Graduate School at the Weizmann Institute, Israel. A. H. Wright is supported by an European Research Council Consolidator Grant (770935). \n\nThe Palomar Transient Factory project is a scientific collaboration among the California Institute of Technology, Los Alamos National Laboratory, the University of Wisconsin, Milwaukee, the Oskar Klein Center, the Weizmann Institute of Science, the TANGO Program of the University System of Taiwan, and the Kavli Institute for the Physics and Mathematics of the Universe. LANL participation in iPTF is supported by the US Department of Energy as a part of the Laboratory Directed Research and Development program. \n\nThis work makes use of data from the Las Cumbres Observatory network. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA; the observatory was made possible by the generous financial support of the W. M. Keck Foundation. Research at Lick Observatory is partially supported by a generous gift from Google. We thank the staffs of the various observatories at which data were obtained for their excellent assistance. \n\nFunding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS web site is www.sdss.org. \n\nSDSS-IV is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration, including the Brazilian Participation Group, the Carnegie Institution for Science, Carnegie Mellon University, the Chilean Participation Group, the French Participation Group, HarvardSmithsonian Center for Astrophysics, Instituto de Astrofísica de Canarias, The Johns Hopkins University, Kavli Institute for the Physics and Mathematics of the Universe (IPMU) / University of Tokyo, Lawrence Berkeley National Laboratory, Leibniz Institut für Astrophysik Potsdam (AIP), Max-Planck-Institut für Astronomie (MPIA Heidelberg), Max-Planck-Institut für Astrophysik (MPA Garching), Max-Planck-Institut für Extraterrestrische Physik (MPE), National Astronomical Observatories of China, New Mexico State University, New York University, University of Notre Dame, Observatário Nacional / MCTI, The Ohio State University, Pennsylvania State University, Shanghai Astronomical Observatory, United Kingdom Participation Group, Universidad Nacional Autónoma de México, University of Arizona, University of Colorado Boulder, University of Oxford, University of Portsmouth, University of Utah, University of Virginia, University of Washington, University of Wisconsin, Vanderbilt University, and Yale University. \n\nThe Pan-STARRS1 Surveys (PS1) have been made possible through contributions of the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, Queen’s University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under Grant NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation under Grant AST-1238877, the University of Maryland, and Eotvos Lorand University (ELTE). \n\nThis publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. \n\nThis publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. \n\nThe LBNL Physics Division is supported by the U.S. Department of Energy Office of Science High Energy\nPhysics. \n\nThe Cerro Tololo Inter-American Observatory and the National Optical Astronomy Observatory are operated by the Association of Universities for Research in Astronomy (AURA) under cooperative agreement with the National Science Foundation. \n\nThe National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract DE-AC02-05CH11231, provided staff, computational resources, and data storage for this project. \n\nThe Computational HEP program in The Department of Energy’s Science Office of High Energy Physics provided resources through the “Cosmology Data Repository” project (Grant #KA2401022). \n\nThe data presented here were obtained in part with ALFOSC, which is provided by the Instituto de Astrofísica de Andalucía (IAA) under a joint agreement with the University of Copenhagen and NOTSA. \n\nSoftware: Astropy version 3.2.3 (Astropy Collaboration et al. 2013, 2018), Flexible Stellar Population Synthesis (FSPS; Conroy et al. 2009), High Order Transform of Psf ANd Template Subtraction version 5.1.11 (Hotpants; Becker 2015), IRAF (Tody 1986), LAMBDAR (Wright et al. 2016), Prospector version 0.3 (Leja et al. 2017), python-fsps (Foreman-Mackey et al. 2014) scikitlearn version 0.21.2 (Pedregosa et al. 2011), Software for Calibrating AstroMetry and Photometry (SCAMP; Bertin 2006) version 2.0.4, Source Extractor version 2.19.5 (Bertin & Arnouts 1996), Supernova Identification version 5.0 (Blondin & Tonry 2007), Superfit version 3.5 (Howell et al. 2005)", revision_no = "22", abstract = "Several thousand core-collapse supernovae (CCSNe) of different flavors have been discovered so far. However, identifying their progenitors has remained an outstanding open question in astrophysics. Studies of SN host galaxies have proven to be powerful in providing constraints on the progenitor populations. In this paper, we present all CCSNe detected between 2009 and 2017 by the Palomar Transient Factory. This sample includes 888 SNe of 12 distinct classes out to redshift z ≈ 1. We present the photometric properties of their host galaxies from the far-ultraviolet to the mid-infrared and model the host-galaxy spectral energy distributions to derive physical properties. The galaxy mass functions of Type Ic, Ib, IIb, II, and IIn SNe ranges from 10⁵ to 10^(11.5) M_⊙, probing the entire mass range of star-forming galaxies down to the least-massive star-forming galaxies known. Moreover, the galaxy mass distributions are consistent with models of star-formation-weighted mass functions. Regular CCSNe are hence direct tracers of star formation. Small but notable differences exist between some of the SN classes. Type Ib/c SNe prefer galaxies with slightly higher masses (i.e., higher metallicities) and star-formation rates than Type IIb and II SNe. These differences are less pronounced than previously thought. H-poor SLSNe and SNe~Ic-BL are scarce in galaxies above 10¹⁰ M_⊙. Their progenitors require environments with metallicities of <0.4 and <1 solar, respectively. In addition, the hosts of H-poor SLSNe are dominated by a younger stellar population than all other classes of CCSNe. Our findings corroborate the notion that low-metallicity and young age play an important role in the formation of SLSN progenitors.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105422, title ="SN 2020bqj: a Type Ibn supernova with a long lasting peak plateau", author = "Kool, E. C. and Karamehmetoglu, E.", journal = "arXiv", month = "August", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200916-112927301", note = "ECK acknowledges support from the G.R.E.A.T research environment funded by Vetenskapsrådet, the Swedish Research Council, under project number 2016-06012, and support from The Wenner-Gren Foundations. RL is supported by a Marie Skłodowska-Curie Individual Fellowship within the Horizon 2020 European Union (EU) Framework Programme for Research\nand Innovation (H2020-MSCA-IF-2017-794467). ESP’s research was funded in part by the Gordon and Betty Moore Foundation through Grant GBMF5076. Y-LK has received funding from the European Research Council (ERC) under the European Unions Horizon 2020 research and innovation program (grant agreement No. 759194 USNAC). MLG acknowledges support from the DiRAC Institute in the Department of Astronomy at the University of Washington. AH is grateful for the support by grants from the Israel Science Foundation, the US-Israel Binational Science Foundation, and the I-CORE Program of the Planning and Budgeting Committee and the Israel Science Foundation. \n\nBased on observations obtained with the Samuel Oschin 48-inch Telescope and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project, a scientific collaboration among the California Institute of Technology, the Oskar Klein Centre, the Weizmann Institute of Science, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron, the University of Wisconsin-Milwaukee, and the TANGO Program of the University System of Taiwan. Further support is provided by the U.S. National Science Foundation under Grant No. AST-1440341. \n\nThis work is based in part on observations made with the Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. \n\nThis research uses services or data provided by the Astro Data Lab at NSF’s National Optical-Infrared Astronomy Research Laboratory. NSF’s OIR Lab is operated by the Association of Universities for Research in Astronomy (AURA), Inc. under a cooperative agreement with the National Science Foundation. \n\nThe Photometric Redshifts for the Legacy Surveys (PRLS) catalog used in this paper was produced thanks to funding from the U.S. Department of Energy Office of Science, Office of High Energy Physics via grant DE-SC0007914. \n\nThe data presented here were obtained in part with ALFOSC, which is provided by the Instituto de Astrofisica de Andalucia (IAA-CSIC) under a joint agreement with the University of Copenhagen and NOTSA The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council. \n\nSED Machine is based upon work supported by the National Science Foundation under Grant No. 1106171. \n\nThis work was supported by the GROWTH project funded by the National Science Foundation under Grant No 1545949. \n\nThe ZTF forced-photometry service was funded under the Heising-Simons Foundation grant #12540303 (PI: Graham). \n\nWe would like to thank participating observers on the UW APO ZTF followup team, including: Brigitta Spiőcz, Keaton Bell, and James Davenport. The DiRAC Institute is supported through generous gifts from the Charles and Lisa Simonyi Fund for Arts and Sciences, and the Washington Research Foundation. \n\nWe thank the staff of the Mullard Radio Astronomy Observatory, University of Cambridge, for their support in the maintenance, and operation of AMI. We acknowledge support from the European Research Council under grant ERC-2012-StG-307215 LODESTONE.", revision_no = "15", abstract = "Context. Type Ibn supernovae (SNe Ibn) are a rare class of stripped envelope supernovae interacting with a helium-rich circumstellar medium (CSM). The majority of the SNe Ibn reported in the literature display a surprising homogeneity in their fast-evolving lightcurves and are typically found in actively starforming spiral galaxies. \n\nAims. We present the discovery and the study of SN 2020bqj (ZTF20aalrqbu), a SN Ibn with a long-duration peak plateau lasting 40 days and hosted by a faint low-mass galaxy. We aim to explain its peculiar properties using an extensive photometric and spectroscopic data set. \n\nMethods. We compare the photometric and spectral evolution of SN 2020bqj with regular SNe Ibn from the literature, as well as with other outliers in the SN Ibn subclass. We fit the bolometric and multi-band lightcurves with powering mechanism models such as radioactive decay and CSM interaction. We also model the host galaxy of SN 2020bqj. \n\nResults. The risetime, peak magnitude and spectral features of SN 2020bqj are consistent with those of most SNe Ibn, but the SN is a clear outlier in the subclass based on its bright, long-lasting peak plateau and the low mass of its faint host galaxy. We show through modeling that the lightcurve of SN 2020bqj can be powered predominantly by shock heating from the interaction of the SN ejecta and a dense CSM. The peculiar Type Ibn SN 2011hw is a close analog to SN 2020bqj in terms of lightcurve and spectral evolution, suggesting a similar progenitor and CSM scenario. In this scenario a very massive progenitor star in the transitional phase between a luminous blue variable and a compact Wolf-Rayet star undergoes core-collapse, embedded in a dense helium-rich CSM with an elevated opacity compared to normal SNe Ibn, due to the presence of residual hydrogen. This scenario is consistent with the observed properties of SN 2020bqj and the modeling results.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105430, title ="Tidally Trapped Pulsations in Binary Stars", author = "Fuller, J. and Kurtz, D. W.", journal = "arXiv", month = "August", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200916-112956523", note = "We thank the anonymous referee for a thorough review of this manuscript. This research was supported in part by the National Science Foundation under Grant No. NSF PHY-1748958. JF is thankful for support through an Innovator Grant from The Rose Hills Foundation, and the Sloan Foundation through grant FG-2018-10515. GH gratefully acknowledges funding through NCN grant 2015/18/A/ST9/00578. \n\nDATA AVAILABILITY. Data and source code is available upon request to the authors.", revision_no = "9", abstract = "A new class of pulsating binary stars was recently discovered, whose pulsation amplitudes are strongly modulated with orbital phase. Stars in close binaries are tidally distorted, so we examine how a star's tidally induced asphericity affects its oscillation mode frequencies and eigenfunctions. We explain the pulsation amplitude modulation via tidal mode coupling such that the pulsations are effectively confined to certain regions of the star, e.g., the tidal pole or the tidal equator. In addition to a rigorous mathematical formalism to compute this coupling, we provide a more intuitive semi-analytic description of the process. We discuss three resulting effects: 1. Tidal alignment, i.e., the alignment of oscillation modes about the tidal axis rather than the rotation axis; 2. Tidal trapping, e.g., the confinement of oscillations near the tidal poles or the tidal equator; 3. Tidal amplification, i.e., increased flux perturbations near the tidal poles where acoustic modes can propagate closer to the surface of the star. Together, these phenomena can account for the pulsation amplitude and phase modulation of the recently discovered class of \"tidally tilted pulsators.\" We compare our theory to the three tidally tilted pulsators HD 74423, CO Cam, and TIC 63328020, finding that tidally trapped modes that are axisymmetric about the tidal axis can largely explain the first two, while a non-axisymmetric tidally aligned mode is present in the latter. Finally, we discuss implications and limitations of the theory, and we make predictions for the many new tidally tilted pulsators likely to be discovered in the near future.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105190, title ="Constraining the Kilonova Rate with Zwicky Transient Facility Searches Independent of Gravitational Wave and Short Gamma-ray Burst Triggers", author = "Andreoni, Igor and Kool, Erik C.", journal = "arXiv", month = "July", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200901-074328291", note = "We thank P. Nugent for reviewing the manuscript and providing us with useful feedback. We thank D. Perley for useful discussion. Based on observations obtained with the Samuel Oschin 48-inch Telescope and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project, a scientific collaboration among the California Institute of Technology, the Oskar Klein Centre, the Weizmann Institute of Science, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron, the University of Wisconsin-Milwaukee, and the TANGO Program of the University System of Taiwan. Further support is provided by the U.S. National Science Foundation under Grant No. AST-1440341. \n\nThis work was supported by the GROWTH (Global Relay of Observatories Watching Transients Happen) project funded by the National Science Foundation under PIRE Grant No 1545949. GROWTH is a collaborative project among California Institute of Technology (USA), University of Maryland College Park (USA), University of Wisconsin Milwaukee (USA), Texas Tech University (USA), San Diego State University (USA), University of Washington (USA), Los Alamos National Laboratory (USA), Tokyo Institute of Technology (Japan), National Central University (Taiwan), Indian Institute of Astrophysics (India), Indian Institute of Technology Bombay (India), Weizmann Institute of Science (Israel), The Oskar Klein Centre at Stockholm University (Sweden), Humboldt University (Germany), Liverpool John Moores University (UK)\nand University of Sydney (Australia). \n\nE. C. K., A. S. C., and A. G. acknowledge support from the G.R.E.A.T research environment funded by Vetenskapsrådet, the Swedish Research Council, project number 2016-06012. E. C. K. also acknowledges support from The Wenner-Gren Foundations. M. W. C. acknowledges support from the National Science Foundation with grant number PHY-2010970. D. L. K. is supported by NSF grant AST-1816492. \n\nWe thank A. Miller for the star/galaxy classification\ncode development for ZTF. This research has made use of the VizieR catalog access tool, CDS, Strasbourg, France (DOI: 10.26093/cds/vizier). The original description of the VizieR service was published in A&AS 143, 23. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. \n\nSoftware: Astropy (TheAstropyCollaboration2018), Pandas (pandas development team 2020), Matplotlib (Caswell et al. 2020), Kowalski (Duev et al. 2019), lpipe (Perley 2019), PostgreSQL, PyRAF DBSP data reductionpipeline (Bellm&Sesar2016), ztfquery (Rigault2018), SExtractor (Bertin&Arnouts 2010), ForcePhotZTF (Yao et al. 2019).", revision_no = "18", abstract = "The first binary neutron star merger, GW170817, was accompanied by a radioactivity-powered optical/infrared transient called a kilonova. To date, no compelling kilonova has been found during optical surveys of the sky, independent of gravitational-wave triggers. In this work, we searched the first 23 months of the Zwicky Transient Facility (ZTF) data stream for candidate kilonovae in the form of rapidly evolving transients. We combined ZTF alert queries with forced point-spread-function photometry and nightly flux stacking to increase our sensitivity to faint and fast transients. Automatic queries yielded > 11,200 candidates, 24 of which passed quality checks and strict selection criteria based on a grid of kilonova models tailored for both binary neutron star and neutron star-black hole mergers. None of the candidates in our sample was deemed a possible kilonova after thorough vetting, catalog cross-matching, and study of their color evolution. The sources that passed our selection criteria are dominated by Galactic cataclysmic variables. In addition, we identified two fast transients at high Galactic latitude, one of which is the confirmed afterglow of long-duration GRB190106A, and the other is a possible cosmological afterglow. Using a survey simulation code, we constrained the kilonova rate for a range of models including top-hat and linearly decaying light curves and synthetic light curves obtained with radiative transfer simulations. For prototypical GW170817-like kilonovae, we constrain the rate to be R < 1775 Gpc⁻³ yr⁻¹ at 95% confidence level by requiring at least 2 high-significance detections. By assuming a population of kilonovae with the same geometry and composition of GW170817 observed under a uniform viewing angle distribution, we obtained a constraint on the rate of R < 4029 Gpc⁻³ yr⁻¹.", } @misc {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105429, title ="The Saturn Ring Skimmer Mission Concept: The next step to explore Saturn's rings, atmosphere, interior and inner magnetosphere", author = "Tiscareno, Matthew S. and Vaquero, Mar", month = "July", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200916-112953100", note = "A white paper to be submitted to the 2023 Planetary Science Decadal Survey.", revision_no = "10", abstract = "The innovative Saturn Ring Skimmer mission concept enables a wide range of investigations that address fundamental questions about Saturn and its rings, as well as giant planets and astrophysical disk systems in general. This mission would provide new insights into the dynamical processes that operate in astrophysical disk systems by observing individual particles in Saturn's rings for the first time. The Ring Skimmer would also constrain the origin, history, and fate of Saturn's rings by determining their compositional evolution and material transport rates. In addition, the Ring Skimmer would reveal how the rings, magnetosphere, and planet operate as an inter-connected system by making direct measurements of the ring's atmosphere, Saturn's inner magnetosphere and the material owing from the rings into the planet. At the same time, this mission would clarify the dynamical processes operating in the planet's visible atmosphere and deep interior by making extensive high-resolution observations of cloud features and repeated measurements of the planet's extremely dynamic gravitational field. Given the scientific potential of this basic mission concept, we advocate that it be studied in depth as a potential option for the New Frontiers program.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/104978, title ="HAT-P-58b -- HAT-P-64b: Seven Planets Transiting Bright Stars", author = "Bakos, G. Á. and Hartman, J. D.", journal = "arXiv", month = "July", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200817-104917526", note = "Based on observations of the Hungarian-made Automated Telescope Network and observations obtained at the following observatories: W. M. Keck Observatory, the 1.5m and the 1.2m telescopes at the Fred Lawrence Whipple Observatory of the Smithsonian Astrophysical Observatory, the Kitt Peak National Observatory, the 1.93m telescope at Observatoire de Haute-Provence,\nthe Subaru Telescope of the National Astronomical Observatory\nof Japan, the Nordic Optical Telescope in the Spanish Observatorio del Roque de los Muchachos of the Intituto de Astrofisica de Canarias, and the Apache Point Observatory 3.5m telescope. \n\nHATNet operations have been funded by\nNASA grants NNG04GN74G, NNX08AF23G, and\nNNX13AJ15G. Follow-up of HATNet targets has been\npartially supported through NSF grant AST-1108686.\nG._A.B, J.H., Z.C. and K.P. acknowledge partial support\nfrom NASA grant NNX17AB61G. G.B. acknowledges\nsupport from the Hungarian Academy of Sciences, and\nthanks for the warm hospitality of Konkoly Observatory\nin carrying out some of his research. J.H. acknowledges\nsupport from NASA grant NNX14AF87G. K.P. acknowledges\nsupport from NASA grant 80NSSC18K1009.\nG.K. thanks the support from the National Research,\nDevelopment and Innovation Office (grant K 129249).\nWe acknowledge partial support also from the Kepler\nMission under NASA Cooperative Agreement\nNNX13AB58A (D.W.L., PI). Data presented in this\npaper are based on observations obtained at the HAT\nstation at the Submillimeter Array of SAO, and the\nHAT station at the Fred Lawrence Whipple Observatory\nof SAO. We acknowledge J.A. Johnson in supporting\nthe Keck HIRES observations. The authors wish\nto acknowledge the very significant cultural role and\nreverence that the summit of Mauna Kea has always\nhad within the indigenous Hawaiian community. We\nare most fortunate to have the opportunity to conduct\nobservations from this mountain. This research\nhas made use of Keck telescope time granted through\nNOAO (programs: A245Hr, A202Hr; PI: G.B) and\nNASA (programs: N154Hr, N133Hr, N136Hr, N143Hr,\nN169Hr, N186Hr; PI: G.B). Based on observations at\nKitt Peak National Observatory, National Optical Astronomy\nObservatory (NOAO Prop. ID: 2015B-0156;\nPI: J.H.), which is operated by the Association of Universities\nfor Research in Astronomy (AURA) under a\ncooperative agreement with the National Science Foundation.\nBased on radial velocities obtained with the\nSOPHIE spectrograph mounted on the 1.93m telescope\nat Observatoire de Haute-Provence. Based on data collected\nat Subaru Telescope, which is operated by the\nNational Astronomical Observatory of Japan. Based on\nobservations made with the Nordic Optical Telescope,\noperated on the island of La Palma jointly by Denmark,\nFinland, Norway, Sweden, in the Spanish Observatorio\ndel Roque de los Muchachos of the Intituto de Astrofisica de Canarias. Based on observations obtained\nwith the Apache Point Observatory 3.5m telescope,\nwhich is owned and operated by the Astrophysical Research\nConsortium. This research was made possible\nthrough the use of the AAVSO Photometric All-Sky\nSurvey (APASS), funded by the Robert Martin Ayers\nSciences Fund. This research has made use of the NASA\nExoplanet Archive, which is operated by the California\nInstitute of Technology, under contract with the National\nAeronautics and Space Administration under the\nExoplanet Exploration Program.", revision_no = "11", abstract = "We report the discovery and characterization of 7 transiting exoplanets from the HATNet survey. The planets, which are hot Jupiters and Saturns transiting bright sun-like stars, include: HAT-P-58b (with mass M_p = 0.37 M_J, radius R_p = 1.33 R_J, and orbital period P = 4.0138 days), HAT-P-59b (M_p = 1.54 M_J, R_p = 1.12 R_J, P = 4.1420 days), HAT-P-60b (M_p = 0.57 M_J, R_p = 1.63 R_J, P = 4.7948 days), HAT-P-61b (M_p = 1.06 M_J, R_p = 0.90 R_J, P = 1.9023 days), HAT-P-62b (M_p = 0.76 M_J, R_p = 1.07 R_J, P = 2.6453 days), HAT-P-63b (M_p = 0.61 M_J, R_p = 1.12 R_J, P = 3.3777 days), and HAT-P-64b (M_p = 0.58 M_J, R_p = 1.70 R_J, P = 4.0072 days). The typical errors on these quantities are 0.06 M_J, 0.03 R_J, and 0.2 seconds, respectively. We also provide accurate stellar parameters for each of the hosts stars. With V = 9.710±0.050mag, HAT-P-60 is an especially bright transiting planet host, and an excellent target for additional follow-up observations. With Rp = 1.703±0.070 R_J, HAT-P-64b is a highly inflated hot Jupiter around a star nearing the end of its main-sequence lifetime, and is among the largest known planets. Five of the seven systems have long-cadence observations by TESS which are included in the analysis. Of particular note is HAT-P-59 (TOI-1826.01) which is within the Northern continuous viewing zone of the TESS mission, and HAT-P-60, which is the TESS candidate TOI-1580.01.", } @misc {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105410, title ="International Coordination of Multi-Messenger Transient Observations in the 2020s and Beyond: Kavli-IAU White Paper", author = "Cenko, S. Bradley and Whitelock, Patricia A.", journal = "arXiv", month = "July", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200916-112843963", note = "We are very grateful to the Kavli Foundation for a very generous donation that made the workshop possible. Thanks to the South African Radio Astronomy Observatory (SARAO) for their sponsorship of social events, and the SAAO for their superb organization and hospitality. In particular we are grateful to Christian Hettlage for his management of the IT associated with the meeting, to Nazli Mohamed for handling registration and most of the organizational details, to Glenda Snowball for dealing with the finance, and to Valencia Cloete for arranging the trip to Sutherland. Thanks also to Jessymol Thomas and the following students for their help with the presentations: Miriam Nyamai, Simon de Wet, David Modiano, Danté Hewitt, Irvin Martínez and Orapeleng Mogawana.", revision_no = "8", abstract = "This White Paper summarizes the discussions from a five-day workshop, involving 50 people from 18 countries, held in Cape Town, South Africa in February 2020. Convened by the International Astronomical Union's Executive Committee Working Group on Global Coordination of Ground and Space Astrophysics and sponsored by the Kavli Foundation, we discussed existing and potential bottlenecks for transient and multi-messenger astronomy, identifying eight broad areas of concern. Some of these are very similar to the challenges faced by many astronomers engaging in international collaboration, for example, data access policies, funding, theoretical and computational resources and workforce equity. Others, including, alerts, telescope coordination and target-of-opportunity implementation, are strongly linked to the time domain and are particularly challenging as we respond to transients. To address these bottlenecks we offer thirty-five specific recommendations, some of which are simply starting points and require development. These recommendations are not only aimed at collaborative groups and individuals, but also at the various organizations who are essential to making transient collaborations efficient and effective: including the International Astronomical Union, observatories, projects, scientific journals and funding agencies. We hope those involved in transient research will find them constructive and use them to develop collaborations with greater impact and more inclusive teams.", } @misc {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/104980, title ="EarthFinder Probe Mission Concept Study: Characterizing nearby stellar exoplanet systems with Earth-mass analogs for future direct imaging", author = "Plavchan, Peter and Vasisht, Gautam", journal = "arXiv", month = "June", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200817-122112681", note = "© 2019. \n\nNASA Probe Mission concept white paper for 2020 Astrophysics National Academies Decadal Survey. \n\nThis research was carried out at George Mason University and the Jet Propulsion\nLaboratory, California Institute of Technology, under a contract with the National\nAeronautics and Space Administration.\nReference herein to any specific commercial product, process, or service by trade\nname, trademark, manufacturer, or otherwise, does not constitute or imply its\nendorsement by the United States Government or the Jet Propulsion Laboratory,\nCalifornia Institute of Technology.", revision_no = "8", abstract = "EarthFinder is a NASA Astrophysics Probe mission concept selected for study as input to the 2020 Astrophysics National Academies Decadal Survey. The EarthFinder concept is based on a dramatic shift in our understanding of how PRV measurements should be made. We propose a new paradigm which brings the high precision, high cadence domain of transit photometry as demonstrated by Kepler and TESS to the challenges of PRV measurements at the cm/s level. This new paradigm takes advantage of: 1) broad wavelength coverage from the UV to NIR which is only possible from space to minimize the effects of stellar activity; 2) extremely compact, highly stable, highly efficient spectrometers (R>150,000) which require the diffraction-limited imaging possible only from space over a broad wavelength range; 3) the revolution in laser-based wavelength standards to ensure cm/s precision over many years; 4) a high cadence observing program which minimizes sampling-induced period aliases; 5) exploiting the absolute flux stability from space for continuum normalization for unprecedented line-by-line analysis not possible from the ground; and 6) focusing on the bright stars which will be the targets of future imaging missions so that EarthFinder can use a ~1.5 m telescope.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/104099, title ="The Keck Baryonic Structure Survey: Using foreground/background galaxy pairs to trace the structure and kinematics of circumgalactic neutral hydrogen at z ∼ 2", author = "Chen, Yuguang and Steidel, Charles C.", journal = "arXiv", month = "June", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200626-150116926", note = "Based on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. \n\nThis paper has included data obtained using Keck/LRIS (Oke et al. 1995; Steidel et al. 2004; Rockosi et al. 2010) and Keck/MOSFIRE (McLean et al. 2010, 2012). We thank the W.M. Keck Observatory staff for their assistance with the observations over two decades. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. \n\nThe following software packages have been crucial to preparing for this paper: the IDL Astronomy User's Library14, the Coyote IDL library15, Astropy (Price-Whelan et al. 2018), Emcee (Foreman-Mackey et al. 2013), the yt project (Turk et al. 2011), and Trident (Hummels et al. 2017). \n\nThis work was supported in part by grant AST-1313472 from the U.S. NSF, and by a grant from the Caltech/JPL President's and Director's Program. CAFG was supported by NSF through grants AST-1517491, AST-1715216, and CAREER award AST-1652522, by NASA through grant 17-ATP17-0067, by STScI through grants HST-GO-14681.011, HST-GO-14268.022-A, and HST-AR-14293.001-A, and by a Cottrell Scholar Award from the Research Corporation for Science Advancement. \n\nYC would like to thank Hongjie Zhu, for her continuous encouragements when preparing for this paper. We would like to acknowledge YiqiuMa, E. Sterl Phinney, and Mateusz Matuszewski, for their constructive discussions. Finally, we thank collaborators Kurt L. Adelberger, Matthew P. Hunt, David R. Law, Olivera Rakic, and Monica L. Turner for their contributions to the KBSS survey over the course of nearly two decades.", revision_no = "11", abstract = "We present new measurements of the spatial distribution and kinematics of neutral hydrogen in the circumgalactic and intergalactic medium surrounding star-forming galaxies at z ~ 2. Using the spectra of ~ 3000 galaxies with redshifts ± 0.4 from the Keck Baryonic Structure Survey (KBSS), we assemble a sample of more than 200,000 distinct foreground-background pairs with projected angular separations of 3 - 500 arcsec and spectroscopic redshifts, with = 2.23 and = 2.57. The ensemble of sightlines and foreground galaxies is used to construct a 2D map of the mean excess Lyα optical depth relative to the intergalactic mean as a function of projected galactocentric distance (20 < D_(tran)/pkpc ≾ 4000) and line-of-sight velocity. We provide information on the line-of-sight kinematics of H I gas as a function of projected distance D_(tran). We compare the map with cosmological zoom-in simulation, finding qualitative agreement between them. A simple two-component (accretion, outflow) analytical model generally reproduces the observed line-of-sight kinematics and projected spatial distribution of H I. The best-fitting model suggests that galaxy-scale outflows with initial velocity v_(out) ≃ 600 km s⁻¹ dominate the kinematics of circumgalactic H I out to Dtran ~ 50 kpc, while H I at D_(tran) ≳ 100 kpc is dominated by infall with characteristic v_(in) ≾ v_c, where v_c is the circular velocity of the host halo (M_h ~ 10¹² M_⊙). Over the impact parameter range 80 ≾ D_(tran)/pkpc < 200, the H I line-of-sight velocity range reaches a minimum, with a corresponding flattening in the rest-frame Lyα equivalent width. These observations can be naturally explained as the transition between outflow-dominated and accretion-dominated flows. Beyond D_(tran) ≃ 300 kpc, the line of sight kinematics are dominated by Hubble expansion.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105068, title ="Kilonova Luminosity Function Constraints based on Zwicky Transient Facility Searches for 13 Neutron Star Mergers", author = "Kasliwal, Mansi M. and Anand, Shreya", journal = "arXiv", month = "June", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200824-085517593", note = "This work was supported by the GROWTH (Global\nRelay of Observatories Watching Transients Happen)\nproject funded by the National Science Foundation under PIRE Grant No 1545949. GROWTH is a collaborative project among California Institute of Technology\n(USA), University of Maryland College Park (USA),\nUniversity of Wisconsin Milwaukee (USA), Texas Tech\nUniversity (USA), San Diego State University (USA),\nUniversity of Washington (USA), Los Alamos National Laboratory (USA), Tokyo Institute of Technology\n(Japan), National Central University (Taiwan), Indian\nInstitute of Astrophysics (India), Indian Institute of\nTechnology Bombay (India), Weizmann Institute of Science (Israel), The Oskar Klein Centre at Stockholm\nUniversity (Sweden), Humboldt University (Germany),\nLiverpool John Moores University (UK) and University\nof Sydney (Australia). Based on observations obtained\nwith the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of\nthe Zwicky Transient Facility project. ZTF is supported\nby the National Science Foundation under Grant No.\nAST-1440341 and a collaboration including Caltech,\nIPAC, the Weizmann Institute for Science, the Oskar\nKlein Center at Stockholm University, the University\nof Maryland, the University of Washington, Deutsches\nElektronen-Synchrotron and Humboldt University, Los\nAlamos National Laboratories, the TANGO Consortium\nof Taiwan, the University of Wisconsin at Milwaukee,\nand Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. The\nZTF forced-photometry service was funded under the\nHeising-Simons Foundation grant #12540303 (PI: Graham). SED Machine is based upon work supported\nby the National Science Foundation under Grant No.\n1106171.\nGROWTH India telescope is a 70-cm telescope with\na 0.7 degree field of view, set up by the Indian Institute\nof Astrophysics and the Indian Institute of Technology Bombay with support from the Indo-US Science\nand Technology Forum (IUSSTF) and the Science and\nEngineering Research Board (SERB) of the Department of Science and Technology (DST), Government\nof India (https://sites.google.com/view/growthindia/).\nIt is located at the Indian Astronomical Observatory\n(Hanle), operated by the Indian Institute of Astrophysics (IIA). GROWTH-India project is supported\nby SERB and administered by IUSSTF, under grant\nnumber IUSSTF/PIRE Program/GROWTH/2015-16. This research has made use of the VizieR catalogue access tool, CDS, Strasbourg, France (DOI :\n10.26093/cds/vizier). The original description of the\nVizieR service was published in A&AS 143, 23. These\nresults made use of the Lowell Discovery Telescope\n(LDT) at Lowell Observatory. Lowell is a private, non-profit institution dedicated to astrophysical research\nand public appreciation of astronomy and operates the\nLDT in partnership with Boston University, the University of Maryland, the University of Toledo, Northern\nArizona University and Yale University. The Large\nMonolithic Imager was built by Lowell Observatory\nusing funds provided by the National Science Foundation (AST-1005313). The upgrade of the DeVeny\noptical spectrograph has been funded by a generous\ngrant from John and Ginger Giovale and by a grant\nfrom the Mt. Cuba Astronomical Foundation. The\nKPED team thanks the National Science Foundation\nand the National Optical Astronomical Observatory for\nmaking the Kitt Peak 2.1-m telescope available. We\nthank the observatory staff at Kitt Peak for their efforts\nto assist Robo-AO KP operations. The KPED team\nthanks the National Science Foundation, the National\nOptical Astronomical Observatory, the Caltech Space\nInnovation Council and the Murty family for support in\nthe building and operation of KPED. In addition, they\nthank the CHIMERA project for use of the Electron\nMultiplying CCD (EMCCD). The Liverpool Telescope\nis operated on the island of La Palma by Liverpool\nJohn Moores University in the Spanish Observatorio del\nRoque de los Muchachos of the Instituto de Astrofisica\nde Canarias with financial support from the UK Science\nand Technology Facilities Council. Some spectroscopic\nobservations were obtained with the Southern African\nLarge Telescope (SALT). The Photometric Redshifts for\nthe Legacy Surveys (PRLS) catalog used in this paper\nwas produced thanks to funding from the U.S. Department of Energy Office of Science, Office of High Energy\nPhysics via grant DE-SC0007914. This publication has\nmade use of data collected at Lulin Observatory, partly\nsupported by MoST grant 108-2112-M-008-001. Based\non observations made with the Gran Telescopio Canarias (GTC), installed at the Spanish Observatorio del\nRoque de los Muchachos of the Instituto de Astrofisica\nde Canarias, in the island of La Palma.\nM. W. C. acknowledges support from the National\nScience Foundation with grant number PHY-2010970.\nA. G. and J. S. acknowledge support from the Knut\nand Alice Wallenberg Foundation and the GREAT re-\nsearch environment grant 2016-06012, funded by the\nSwedish Research Council. Some of the work by D. A. P.\nwas performed at the Aspen Center for Physics, which\nis supported by National Science Foundation grant\nPHY-1607611. D. A. P. was partially supported by\na grant from the Simons Foundation. H. K. thanks\nthe LSSTC Data Science Fellowship Program, which is\nfunded by LSSTC, NSF Cybertraining Grant 1829740,\nthe Brinson Foundation, and the Moore Foundation;\nhis participation in the program has benefited this\nwork. This work has been supported by the Spanish\nScience Ministry Centro de Excelencia Severo Ochoa\nProgram under grant SEV-2017-0709. AJCT acknowledges support from the Junta de Andalucía (Project\nP07-TIC-03094) and support from the Spanish Ministry\nProjects AYA2012-39727-C03-01, AYA2015-71718R and\nPID2019-109974RB-I00. VAF was supported by RFBR\n19-02-00432 grant. I.A. acknowledges support by a\nRamón y Cajal grant (RYC-2013-14511) of the Ministerio de Ciencia, Innovación, y Universidades (MICIU)\nof Spain. He also acknowledges financial support from\nMCIU through grant AYA2016-80889-P. A. A. M. is\nfunded by the Large Synoptic Survey Telescope Corporation, the Brinson Foundation, and the Moore Foundation in support of the LSSTC Data Science Fellowship\nProgram; he also receives support as a CIERA Fellow\nby the CIERA Postdoctoral Fellowship Program (Center for Interdisciplinary Exploration and Research in\nAstrophysics, Northwestern University). A. C. acknowledges support from the National Science Foundation\nwith grant #1907975. W.-H. I., A. K., K.-L. L., C.-C. N., A. P., H. T. and P.-C. Y. acknowledge the support from MoST (Ministry of Science and Technology,\nTaiwan) grants 104-2923-M-008-004-MY5, 107-2119-M-008-012, 108-2628-M-007-005-RSP and 108-2112-M-007-025-MY3. D. Dobie is supported by an Australian Government Research Training Program Scholarship. S.A.\nis supported by GROWTH (Global Relay of Observatories Watching Transients Happen) project funded by\nthe National Science Foundation under PIRE Grant No\n1545949. A.S.C. is supported by the GREAT research\nenvironment grant 2016-06012, funded by the Swedish\nResearch Council. E. C. K. acknowledges support from\nthe G.R.E.A.T. research environment and from The\nWenner-Gren Foundations. A. J. C. T. thanks fruitful\ndiscussions with J. Cepa, E. Fernández-García, J. A.\nFont, S. Jeong, A. Martín-Carrillo, A. M. Sintes, and\nS. Sokolov. D.A.H.B. acknowledges research support\nfrom the National Research Foundation of South Africa.\nS. B. P. and V. B. acknowledge BRICS grant number\n'DST/IMRCD/BRICS/PilotCall1/ProFCheap/2017(G)'\nfor part of the present work. J. S. B was partially supported by a Gordon and Betty Moore Foundation Data-\nDriven Discovery grant and a grant from the National\nScience Foundation, \"Conceptualization of a Scalable\nCyberinfrastructure Center for Multimessenger Astrophysics.\"", revision_no = "26", abstract = "We present a systematic search for optical counterparts to 13 gravitational wave (GW) triggers involving at least one neutron star during LIGO/Virgo's third observing run (O3). We searched binary neutron star (BNS) and neutron star black hole (NSBH) merger localizations with the Zwicky Transient Facility (ZTF) and undertook follow-up with the Global Relay of Observatories Watching Transients Happen (GROWTH) collaboration. The GW triggers had a median localization area of 4480 deg², median distance of 267Mpc and false alarm rates ranging from 1.5 yr⁻¹ to 10⁻²⁵ yr⁻¹. The ZTF coverage had a median enclosed probability of 39%, median depth of 20.8 mag, and median time lag between merger and the start of observations of 1.5 hr. The O3 follow-up by the GROWTH team comprised 340 UltraViolet/Optical/InfraRed (UVOIR) photometric points, 64 OIR spectra, and 3 radio images. We find no promising kilonova (radioactivity-powered counterpart) and we show how to convert the upper limits to constrain the underlying kilonova luminosity function. Initially, we assume that all GW triggers are bonafide astrophysical events regardless of false alarm rate and that kilonovae accompanying BNS and NSBH mergers are drawn from a common population, and later, we relax these assumptions. Assuming that all kilonovae are at least as luminous as the discovery magnitude of GW170817 (-16.1 mag), we calculate that our joint probability of detecting zero kilonovae is only 4.2%. If we assume that all kilonovae are brighter than -16.6 mag (extrapolated peak magnitude of GW170817) and fade at a rate of 1 mag day⁻¹ (similar to GW170817), the joint probability of zero detections is 7%. If we separate the NSBH and BNS populations, the joint probability of zero detections, assuming all kilonovae are brighter than -16.6 mag, is 9.7% for NSBH and 7.9% for BNS mergers. Moreover, no more than <57% (<89%) of putative kilonovae could be brighter than -16.6 mag assuming at evolution (fading by 1 mag day⁻¹), at the 90% confidence level. If we further take into account the online terrestrial probability for each GW trigger, we find that no more than <68% of putative kilonovae could be brighter than -16.6 mag. Comparing to model grids, we find that some kilonovae must have M_(ej) < 0.03M⊙ or X_(lan) > 10⁻⁴ or ø > 30° to be consistent with our limits. We look forward to searches in the fourth GW observing run; even 17 neutron star mergers with only 50% coverage to a depth of -16 mag would constrain the maximum fraction of bright kilonovae to <25%.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105070, title ="ZTF20aajnksq (AT2020blt): A Fast Optical Transient at z ≈ 2.9 With No Detected Gamma-Ray Burst Counterpart", author = "Ho, Anna Y. Q. and Perley, Daniel A.", journal = "arXiv", month = "June", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200824-095838244", note = "A.Y.Q.H. would like to thank Udi Nakar for pointing out that dirty fireballs will have a longer rise time than clean fireballs, and Chris Bochenek and Vikram Ravi for useful discussions regarding scintillation of radio point sources. She would also like to thank Steve Schulze, Eran Ofek, and Avishay Gal-Yam, and David Kaplan for their detailed reading of the manuscript. \n\nA.Y.Q.H. and K.D. were supported by the GROWTH project funded by the National Science Foundation under PIRE Grant No. 1545949. A. A. Miller is funded by the Large Synoptic Survey Telescope Corporation, the Brinson Foundation, and the Moore Foundation in support of the LSSTC Data Science Fellowship Program; he also receives support as a CIERA Fellow by the CIERA Postdoctoral Fellowship Program (Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University). C.F. gratefully acknowledges support of his research by the Heising-Simons Foundation (#2018-0907). \n\nA. Goobar acknowledges support from the K & A Wallenberg Foundation, the Swedish Research Council (VR), and the GREAT research environment grant 2016-06012. \n\nBased on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. \n\nZTF is supported by the National Science Foundation under Grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. SED Machine is based upon work supported by the National Science Foundation under Grant No. 1106171. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. Based on observations obtained at the international Gemini Observatory, a program of NSFs OIR Lab, which is managed by the Association of Universities\nfor Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inova çoes e Comunicaçoes (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). \n\nGemini data were processed using the Gemini IRAF package and DRAGONS (Data Reduction for Astronomy from Gemini Observatory North and South). The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias with financial support from the UK Science and Technology Facilities Council.", revision_no = "14", abstract = "We present ZTF20aajnksq (AT2020blt), a fast-fading (Δr = 2.4 mag in Δt = 1.3 days) red (g−r ≈ 0.6 mag) and luminous (M₁₆₂₆ = −25.9) optical transient at z = 2.9 discovered by the Zwicky Transient Facility (ZTF). AT2020blt shares several features in common with afterglows to long-duration gamma-ray bursts (GRBs): (1) an optical light curve well-described by a broken power-law with a break at t_j = 1 day (observer-frame); (2) a luminous (L_X = 10⁴⁶ erg s⁻¹) X-ray counterpart; and (3) luminous (L_ν = 4×10³¹ erg sec⁻¹ Hz−1 at 10 GHz) radio emission. However, no GRB was detected in the 0.74d between the last ZTF non-detection (r > 20.64) and the first ZTF detection (r = 19.57), with an upper limit on the isotropic-equivalent gamma-ray energy release of E_(γ,iso) < 7×10⁵² erg. AT2020blt is thus the third afterglow-like transient discovered without a detected GRB counterpart (after PTF11agg and ZTF19abvizsw) and the second (after ZTF19abvizsw) with a redshift measurement. We conclude that the properties of AT2020blt are consistent with a classical (initial Lorentz factor Γ₀ ≳ 100) on-axis GRB that was missed by high-energy satellites. Furthermore, by estimating the rate of transients with light curves similar to that of AT2020blt in ZTF high-cadence data, we agree with previous results that there is no evidence for an afterglow-like phenomenon that is significantly more common than classical GRBs. We conclude by discussing the status and future of fast-transient searches in wide-field high-cadence optical surveys.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/103981, title ="Tentative Evidence for Water Vapor in the Atmosphere of the Neptune-Size Exoplanet HD 106315 c", author = "Kreidberg, Laura and Mollière, Paul", journal = "arXiv", month = "June", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200624-081951243", note = "Support for HST program GO-15333 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. This work is based [in part] on observations made with the Spitzer Space Telescope, which was operated by the Jet Propulsion Laboratory, California Institute of Technology under acontract with NASA. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. Some of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX13AC07G and by other grants and contracts. \nThis research made use of matplotlib, a Python library for publication quality graphics (Hunter 2007) This research made use of SciPy (Virtanen et al. 2020) This research made use of NumPy (Van Der Walt et al. 2011). \n\nP.M. acknowledges support from the European Research Council under the European Union's Horizon 2020 research and innovation program under grant agreement No. 832428. Y.K. acknowledges support from the European Unions Horizon 2020 Research and Innovation Programme under Grant Agreement 776403. L.K. acknowledge M.R. Line for illuminating discussions.", revision_no = "8", abstract = "We present a transmission spectrum for the Neptune-size exoplanet HD 106315 c from optical to infrared wavelengths based on transit observations from the Hubble Space Telescope/Wide Field Camera 3, K2, and Spitzer. The spectrum shows tentative evidence for a water absorption feature in the 1.1−1.7μm wavelength range with a small amplitude of 30 ppm (corresponding to just 0.8±0.04 atmospheric scale heights). Based on an atmospheric retrieval analysis, the presence of water vapor is tentatively favored with a Bayes factor of 1.7 - 2.6 (depending on prior assumptions). The spectrum is most consistent with either enhanced metallicity, high altitude condensates, or both. Cloud-free solar composition atmospheres are ruled out at >5σ confidence. We compare the spectrum to grids of cloudy and hazy forward models and find that the spectrum is fit well by models with moderate cloud lofting or haze formation efficiency, over a wide range of metallicities (1−100× solar). We combine the constraints on the envelope composition with an interior structure model and estimate that the core mass fraction is ≳0.3. With a bulk composition reminiscent of that of Neptune and an orbital distance of 0.15 AU, HD 106315 c hints that planets may form out of broadly similar material and arrive at vastly different orbits later in their evolution.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/103720, title ="The Panchromatic Afterglow of GW170817: The full uniform dataset, modeling, comparison with previous results and implications", author = "Makhathini, Sphesihle and Mooley, Kunal P.", journal = "arXiv", month = "June", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200604-151511891", note = "The MeerKAT telescope is operated by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation, an agency of the Department of Science and Innovation. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. The authors thank the NRAO staff, especially Mark Claussen and Amy Mioduszewski, for scheduling the VLA observations. The Australia Telescope is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. We thank the staff of the GMRT that made these observations possible. GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. The MeerKAT telescope is operated by the South African Radio Astronomy Observatory, (SARAO), which is a facility of the National Research Foundation (NRF), an agency of the Department of Science and Technology. The authors are grateful to Schuyler van Dyk for helpful discussions. KPM is a Jansky Fellow of the National Radio Astronomy Observatory. DD is supported by an Australian Government Research Training Program Scholarship. TM acknowledges the support of the Australian Research Council through grant DP190100561. Parts of this research were conducted by the Australian Research Council Centre of Excellence for Gravitational Wave Discovery (OzGrav), project number CE170100004. We acknowledge support by the GROWTH (Global Relay of Observatories Watching Transients Happen) project funded by the National Science Foundation PIRE (Partnership in International Research and Education) program under Grant No 1545949. DL acknowledges support from NASA grants 80NSSC18K1729 (Fermi) and NNX17AK42G (ATP), Chandra grant TM9-20002X, and NSF grant AST-1907955. This research has made use of NASA's Astrophysics Data System Bibliographic Services. CF gratefully acknowledges support of his research by the Heising-Simons Foundation. JM acknowledges financial support from the State Agency for Research of the Spanish MCIU through the \"Center of Excellence Severo Ochoa\" award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709) and from the grant RTI2018-096228-B-C31 (MICIU/FEDER, EU). DLK was supported by NSF grant AST-1816492 PK is partially supported by the BMBF project 05A17PC2 for D-MeerKAT. \n\nFacility: VLA, ATCA, uGMRT, MeerKAT, eMERLIN, HST, Chandra, XMM-Newton Software: MIRIAD (Sault et al. 1995), CASA (McMullin et al. 2007), emcee (Foreman-Mackey et al. 2013), corner (Foreman-Mackey 2016) , CARACal (Ramatsoku et al. 2020), AOFlagger (Offringa et al. 2010), WSClean (Offringa et al. 2014), CubiCal (Kenyon et al. 2018), MeqTrees (Noordam & Smirnov 2010)", revision_no = "15", abstract = "We present the full panchromatic afterglow light curve data of GW170817, including new radio data as well as archival optical and X-ray data, between 0.5 and 940 days post-merger. By compiling all archival data, and reprocessing a subset of it, we have ensured that the panchromatic dataset is uniform and therefore immune to the differences in data processing or flux determination methods used by different groups. Simple power-law fits to the uniform afterglow light curve indicate a t^(0.86±0.04) rise, a t^(−1.90±0.12) decline, and a peak occurring at 155±4 days. The afterglow is optically thin throughout its evolution, consistent with a single spectral index (−0.569±0.002) across all epochs. This gives a precise and updated estimate of the electron power-law index, p=2.138±0.004. By studying the diffuse X-ray emission from the host galaxy, we place a conservative upper limit on the hot ionized ISM density, <0.01 cm⁻³, consistent with previous afterglow studies. Using the late-time afterglow data we rule out any long-lived neutron star remnant having magnetic field strength between 10^(10.4) G and 10¹⁶ G. Our fits to the afterglow data using an analytical model that includes VLBI proper motion from Mooley et al (2018), and a structured jet model that ignores the proper motion, indicates that the proper motion measurement needs to be considered while seeking an accurate estimate of the viewing angle.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/104100, title ="Pressure balance in the multiphase ISM of cosmologically simulated disk galaxies", author = "Gurvich, Alexander B. and Faucher-Giguère, Claude-André", journal = "arXiv", month = "May", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200626-150120381", note = "AG is grateful to Chang-Goo Kim for very useful discussions regarding the analysis of disk equilibrium in simulations; Samantha Benincasa and Victor Robles for their helpful comments that improved the quality of this paper; and Bridget Haas for her unwavering support and encouragement during the course of the project. AG also acknowledges support from the National Science Foundation under grants DGE-0948017, DGE-145000, and DGE-1842165, and from Blue Waters as a graduate fellow which is itself supported by the National Science Foundation (awards OCI-0725070 and ACI-1238993). CAFG was supported by NSF through grants AST-1412836, AST-1517491, AST-1715216, and CAREER award AST-1652522, by NASA through grants NNX15AB22G and 17-ATP17-0067, by STScI through grants HST-GO-14681.011, HST-GO-14268.022-A, and HST-AR-14293.001-A, and by a Cottrell Scholar Award from the Research Corporation for Science Advancement. AJR was supported by a COFUND/Durham Junior Research Fellowship under EU grant 609412 and by the Science and Technology Facilities Council [ST/P000541/1]. MYG, SW, and JS are supported as a CIERA Fellows by the CIERA Postdoctoral Fellowship Program (Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University). TKC was supported by the Science and Technology Facilities Council astronomy consolidated grant ST/T000244/1. DK was supported by NSF Grant AST-1715101 and by a Cottrell Scholar Award from the Research Corporation for Science Advancement. AW received support from NASA through ATP grant 80NSSC18K1097 and HST grants GO-14734, AR-15057, AR-15809, and GO-15902 from STScI; the Heising-Simons Foundation; and a Hellman Fellowship. Support for SRL was provided by NASA through Hubble Fellowship grant HST-JF2-51395.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. The Flatiron Institute is supported by the Simons Foundation. This research was undertaken, in part, thanks to funding from the Canada Research Chairs program. Numerical calculations were run on the Quest computing cluster at Northwestern University; the Wheeler computing cluster at Caltech; XSEDE allocations TG-AST120025, TG-AST140023, TG-AST130039, and TG-AST140064; Blue Waters PRAC allocation NSF.1713353; and NASA HEC allocation SMD16-7592, SMD-16-7561, SMD-17-1204, SMD-16-7324, and SMD-17-1375.", revision_no = "15", abstract = "Pressure balance plays a central role in models of the interstellar medium (ISM), but whether and how pressure balance is realized in a realistic multiphase ISM is not yet well understood. We address this question using a set of FIRE-2 cosmological zoom-in simulations of Milky Way-mass disk galaxies, in which a multiphase ISM is self-consistently shaped by gravity, cooling, and stellar feedback. We analyze how gravity determines the vertical pressure profile as well as how the total ISM pressure is partitioned between different phases and components (thermal, dispersion/turbulence, and bulk flows). We show that, on average and consistent with previous more idealized simulations, the total ISM pressure balances the weight of the overlying gas. Deviations from vertical pressure balance increase with increasing galactocentric radius and with decreasing averaging scale. The different phases are in rough total pressure equilibrium with one another, but with large deviations from thermal pressure equilibrium owing to kinetic support in the cold and warm phases, which dominate the total pressure near the midplane. Bulk flows (e.g., inflows and fountains) are important at a few disk scale heights, while thermal pressure from hot gas dominates at larger heights. Overall, the total midplane pressure is well-predicted by the weight of the disk gas, and we show that it also scales linearly with the star formation rate surface density (Σ_SFR). These results support the notion that the Kennicutt-Schmidt relation arises because Σ_(SFR) and the gas surface density (Σ_g) are connected via the ISM midplane pressure.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105078, title ="Space VLBI 2020: Science and Technology Futures Conference Summary", author = "Lazio, T. Joseph W. and Brisken, Walter", journal = "arXiv", month = "May", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200824-125712104", note = "© 2020. \n\nWe thank K. Prairie for her expert organization of the conference. This work made use of NASA’s Astrophysics Data System Bibliographic Services. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. The RadioAstron project was led by the Astro Space Center of the Lebedev Physical Institute of the Russian Academy of Sciences and the Lavochkin Scientific and Production Association under a contract with the State Space Corporation ROSCOSMOS, in collaboration with partner organizations in Russia and other countries. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.", revision_no = "10", abstract = "The \"Space VLBI 2020: Science and Technology Futures\" meeting was the second in The Future of High-Resolution Radio Interferometry in Space series. The first meeting (2018 September 5--6; Noordwijk, the Netherlands) focused on the full range of science applications possible for very long baseline interferometry (VLBI) with space-based antennas. Accordingly, the observing frequencies (wavelengths) considered ranged from below 1~MHz (> 300 m) to above 300~GHz (< 1 mm). For this second meeting, the focus was narrowed to mission concepts and the supporting technologies to enable the highest angular resolution observations at frequencies of 30~GHz and higher (< 1 cm).\nThis narrowing of focus was driven by both scientific and technical considerations. First, results from the RadioAstron mission and the Event Horizon Telescope (EHT) have generated considerable excitement for studying the inner portions of black hole (BH) accretion disks and jets and testing elements of the General Theory of Relativity (GR). Second, the technologies and requirements involved in space-based VLBI differ considerably between 100~MHz and 100~GHz; a related consideration is that there are a number of existing instruments or mission concepts for frequencies of approximately 100~MHz and below, while it has been some time since attention has been devoted to space VLBI at frequencies above 10~GHz.\nThis conference summary attempts to capture elements of presentations and discussions that occurred.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/104435, title ="ALMA Characterises the Dust Temperature of z ~ 5.5 Star-Forming Galaxies", author = "Faisst, Andreas L. and Fudamoto, Yoshinobu", journal = "arXiv", month = "May", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200720-071439633", note = "© 2020 The Authors. \n\nThis paper makes use of the following ALMA data: ADS/JAO.ALMA#2018.1.00348.S, ADS/JAO.ALMA#2017.1.00428. L, ADS/JAO.ALMA#2015.1.00388.S, ADS/JAO.ALMA#2015.1. 00928.S, ADS/JAO.ALMA#2012.1.00523.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This work was supported by the Swiss National Science Foundation through the SNSF Professorship grant 157567 ‘Galaxy Build-up at Cosmic Dawn'. D.R. acknowledges support from the National Science Foundation under grant numbers AST-1614213 and AST-1910107. D.R. also acknowledges support from the Alexander von Humboldt Foundation through a Humboldt Research Fellowship for Experienced Researchers.", revision_no = "13", abstract = "The infrared spectral energy distributions (SEDs) of main-sequence galaxies in the early universe (z > 4) is currently unconstrained as infrared continuum observations are time consuming and not feasible for large samples. We present Atacama Large Millimetre Array (ALMA) Band 8 observations of four main-sequence galaxies at z ~ 5.5 to study their infrared SED shape in detail. Our continuum data (rest-frame 110μm, close to the peak of infrared emission) allows us to constrain luminosity weighted dust temperatures and total infrared luminosities. With data at longer wavelengths, we measure for the first time the emissivity index at these redshifts to provide more robust estimates of molecular gas masses based on dust continuum. The Band 8 observations of three out of four galaxies can only be reconciled with optically thin emission redward of rest-frame 100μm. The derived dust peak temperatures at z ~ 5.5 (38±8K) are elevated compared to average local galaxies, however, 5-10K below what would be predicted from an extrapolation of the trend at z < 4. This behaviour can be explained by decreasing dust abundance (or density) towards high redshifts, which would cause the infrared SED at the peak to be more optically thin, making hot dust more visible to the external observer. From the 850μm dust continuum, we derive molecular gas masses between 10¹⁰ and 10¹¹ M⊙ and gas fractions (gas over total mass) of 30-80% (gas depletion times of 100-220Myrs). All in all, our results provide a first measured benchmark SED to interpret future millimetre observations of normal, main-sequence galaxies in the early Universe.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/104102, title ="SatGen: a semi-analytical satellite galaxy generator -- I. The model and its application to Local-Group satellite statistics", author = "Jiang, Fangzhou and Dekel, Avishai", journal = "arXiv", month = "May", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200626-150127283", note = "The authors are thankful to Yuval Birnboim, Timothy Carleton, Nicolas Cournuault, AndrewEmerick, Omri Ginzburg, Sharon Lapiner, Mariangela Lisanti, Lina Necib, Jacob Shen, Oren Slone, and Coral Wheeler for helpful discussions. FJ is supported by the Israeli Planning and Budgeting Committee (PBC) Fellowship, and by the Troesh Fellowship from the California Institute of Technology. FJ is thankful to Jo Bovy for publicly sharing his code design wisdom through the software galpy. FCvdB is supported by the National Aeronautics and Space Administration through Grant Nos. 17-ATP17-0028 and 19-ATP19-0059 issued as part of the Astrophysics Theory Program, and received addition support from the Klaus Tschira foundation. SBG is supported by the US National Science Foundation Graduate Research Fellowship under Grant No. DGE-1752134.", revision_no = "11", abstract = "We present a semi-analytic model of satellite galaxies, SatGen, which can generate large samples of satellite populations for a host halo of desired mass, redshift, and assembly history. The model combines dark-matter halo merger trees, empirical relations for the galaxy-halo connection, and analytic prescriptions for tidal effects, dynamical friction, and ram pressure stripping. SatGen emulates cosmological zoom-in hydro-simulations in certain aspects. Satellites can reside in cored or cuspy DM subhaloes, depending on the halo response to baryonic physics that can be formulated from hydro-simulations and physical modeling. The subhalo profile and the stellar mass and size of a satellite evolves depending on its tidal mass loss and initial structure. The host galaxy can include a baryonic disc and a stellar bulge, each described by a density profile that allows analytic orbit integration. SatGen complements simulations by propagating the effect of halo response found in simulated field galaxies to satellites (not properly resolved in simulations) and outperforms simulations by sampling the halo-to-halo variance of satellite statistics and overcoming artificial disruption due to insufficient resolution. As a first application, we use the model to study satellites of Milky Way sized hosts, making it emulate simulations of bursty star formation and of smooth star formation, respectively, and to experiment with a disc potential in the host halo. Our model reproduces the observed satellite statistics reasonably well. Different physical recipes make a difference in satellite abundance and spatial distribution at the 25% level, not large enough to be distinguished by current observations given the halo-to-halo variance. The MW disc depletes satellites by 20% and has a subtle effect of diversifying the internal structure of satellites, important for alleviating certain small-scale problems. We discuss the conditions for a massive satellite to survive in MW/M31.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/103703, title ="A high-energy neutrino coincident with a tidal disruption event", author = "Stein, Robert and van Velzen, Sjoert", journal = "arXiv", month = "May", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200604-151413064", note = "We thank Cecilia Lunardini, Andrew MacFadyen, Brian Metzger, Andrew Mummery, Alex Pizzuto, Nick Stone, Andrew Taylor andWalterWinter for fruitful discussions. We also thank the IceCube Collaboration for publishing high-energy neutrino alerts. We thank Seth Digel, Ke Fang, Vaidehi Paliya and Judith Racusin for useful feedback provided during Fermi collaboration review. R.S. is grateful to NYU for generously facilitating a visit to develop this work. M.K. is grateful for the hospitality received from Columbia University and NYU during a sabbatical visit. \n\nThis work was supported by the Initiative and Networking Fund of the Helmholtz Association through the Young Investigator Group program (A.F.). \n\nS.v.V is supported by the James Arthur Postdoctoral Fellowship. \n\nThis research was partially supported by the Australian Government through the Australian Research Council’s Discovery Projects funding scheme (project DP200102471). \n\nThe work of M.B. is supported through the South African Research Chair Initiative of the National Research Foundation and the Department of Science and Innovation of South Africa, under SARChI Chair grant No. 64789. \n\nA.H. acknowledges support by the I-Core Program of the Planning and Budgeting Committee and the Israel Science Foundation. \n\nThe UCSC transient team is supported in part by NSF grant AST-1518052, NASA/Swift grant 80NSSC19K1386, the Gordon & Betty Moore Foundation, the Heising-Simons Foundation, and by a fellowship from the David and Lucile Packard Foundation to R.J.F. \n\nV.Z.G. is a Moore-Sloan, WRF Innovation in Data Science, and DIRAC Fellow. \n\nA.G.Y.s research is supported by the EU via ERC grant No. 725161, the ISFGWexcellence center, an IMOS space infrastructure grant and BSF/Transformative and GIF grants, as well as The Benoziyo Endowment Fund for the Advancement of Science, the Deloro Institute for Advanced Research in Space and Optics, The Veronika A. Rabl Physics Discretionary Fund, Paul and Tina Gardner, Yeda-Sela and the WIS-CIT joint research grant; AGY is the recipient of the Helen and Martin Kimmel Award for Innovative Investigation. \n\nM.R. has received funding from the European Research Council (ERC) under the European Unions Horizon 2020 research and innovation program (grant agreement no. 759194 - USNAC). \n\nThe work of D.S. was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. \n\nThe work of S.R. was supported by the Helmholtz Weizmann Research School on Multimessenger Astronomy, funded through the Initiative and Networking Fund of the Helmholtz Association, DESY, the Weizmann Institute, the Humboldt University of Berlin, and the University of Potsdam. \n\nBased on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. SED Machine is based upon work supported by the National Science Foundation under Grant No. 1106171. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. The MeerKAT telescope is operated by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation, an agency of the Department of Science and Innovation. \n\nThis work was supported by the GROWTH (Global Relay of Observatories Watching Transients Happen) project funded by the National Science Foundation Partnership in International Research and Education program under Grant No 1545949. GROWTH is a collaborative project between California Institute of Technology (USA), Pomona College (USA), San Diego State University (USA), Los Alamos National Laboratory (USA), University of Maryland College Park (USA), University of Wisconsin Milwaukee (USA), Tokyo Institute of Technology (Japan), National Central University (Taiwan), Indian Institute of Astrophysics (India), Inter-University Center for Astronomy and Astrophysics (India),Weizmann Institute of Science (Israel), The Oskar Klein Centre at Stockholm University (Sweden), Humboldt University (Germany). \n\nThe Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council Research at Lick Observatory is partially supported by a generous gift from Google. \n\nThe Fermi-LAT Collaboration acknowledges support for LAT development, operation and data analysis from NASA and DOE (United States), CEA/Irfu and IN2P3/CNRS (France), ASI and INFN (Italy), MEXT, KEK, and JAXA (Japan), and the K.A. Wallenberg Foundation, the Swedish Research Council and the National Space Board (Sweden). Science analysis support in the operations phase from INAF (Italy) and CNES (France) is also gratefully acknowledged. This work performed in part under DOE Contract DE-AC02-76SF00515. \n\nAuthor Contributions. R.S. first identified AT2019dsg as a candidate neutrino source, performed the neutrino analysis and was the primary author of the manuscript. M.K., R.S., and S.v.V. developed the multi-zone model. G.F., M.K. and R.S. performed the neutrino modelling. A.F, J.Ne., R.S. and S.R. scheduled and analysed ZTF ToO observations. J.C.A.M.J. and S.v.V. contributed the VLA observations. A.H., R.F., and I.S. contributed the AMI-LA observations. M.Bi., M.Bo., R.F., J.C.A.M.J. and P.W. contributed the MeerKAT observations. The radio analysis was led by S.v.V., with contributions from M.Bi., R.F., A.H., J.C.A.M.J., M.K., R.S, and I.S. S.Ge. and S.v.V. requested and reduced the Swift-UVOT data. D.A.P. and K.T. contributed the LT observations. S.B.C., S.F. and S.Ge. performed X-rays observations and data analysis. S.Ga. analysed Fermi-LAT gamma-ray data. S.R. and S.v.V. analysed the ZTF data. J.B., E.C.B., R.B., S.B.C., V.C., M.F. V.Z.G., A.G., M.J.G, G.H., M.M.K., T.K., R.R.L., A.A.M, F.J.M., H.R., B.R., D.L.S., and M.T.S contributed to the implementation of ZTF. T.A, I.A, M.W.C, M.M.K and L.P.S enabled ZTF ToO observations. A.D., R.J.F., M.J.G., S.Ge., E.H., T.H., M.M.K, C.D.K., M.R., C.R.B., D.S, C.W., and Y.Y contributed to spectroscopic observations and data reduction. R.S. developed the ToO analysis pipeline. V.B., J.No. and J.v.S. developed Ampel, and contributed to the ToO analysis infrastructure. A.G.Y., A.K.H.K., and J.S. contributed to the manuscript and discussions. All authors reviewed the contents of the manuscript. \n\nData availability. Data from Swift and Fermi-LAT satellites, as well as IceCube high-energy neutrino alerts, are already in the public domain (the NASA archive and GCN). Photometry from ZTF, Swift-UVOT, LT and SEDM are provided in the SI (Table S6), along with reduced X-ray data (Table S7) from Swift-XRT and XMM-Newton, that were used to make Figure 1. The radio data from the VLA, AMI-LA, and MeerKAT, that were used to make Figure 2 are provided in the SI (Table S8). \n\nCode availability Python scripts used to perform significant calculations, and make all of the plots, are available on request from R.S. \n\nThe authors declare that they have no competing financial interests.", revision_no = "18", abstract = "Cosmic neutrinos provide a unique window into the otherwise-hidden mechanism of particle acceleration in astrophysical objects. A flux of high-energy neutrinos was discovered in 2013, and the IceCube Collaboration recently associated one high-energy neutrino with a flare from the relativistic jet of an active galaxy pointed towards the Earth. However a combined analysis of many similar active galaxies revealed no excess from the broader population, leaving the vast majority of the cosmic neutrino flux unexplained. Here we present the association of a radio-emitting tidal disruption event (AT2019dsg) with another high-energy neutrino, identified as part of our systematic search for optical counterparts to high-energy neutrinos with the Zwicky Transient Facility (ZTF). The probability of finding any radio-emitting tidal disruption event by chance is 0.5%, while the probability of finding one as bright in bolometric energy flux as AT2019dsg is 0.2%. Our electromagnetic observations can be explained through a multi-zone model, with radio analysis revealing a central engine, embedded in a UV photosphere, that powers an extended synchrotron-emitting outflow. This provides an ideal site for PeV neutrino production. The association suggests that tidal disruption events contribute to the cosmic neutrino flux. Unlike previous work which considered the rare subset of tidal disruption events with relativistic jets, our observations of AT2019dsg suggest an empirical model with a mildly-relativistic outflow.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/103726, title ="Variable Radio AGN at High Redshift Identified in the VLA Sky Survey", author = "Nyland, Kristina and Dong, Dillon", journal = "arXiv", month = "May", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200604-161743307", revision_no = "8", abstract = "As part of an on-going study of radio transients in Epoch 1 (2017-2019) of the Very Large Array Sky Survey (VLASS), we have discovered a sample of 0.2 -17), hydrogen poor events found in the experiment (out of 754 spectroscopically classified SNe). We report the detection of eight Calcium rich gap transients, and place a lower limit on the volumetric rate of these events to be ≈ 15±5% of the SN Ia rate.\nCombining this sample with ten events from the literature, we find evidence of a likely continuum of\nspectroscopic properties ranging from events with SN Ia-like features (Ca-Ia objects) to SN Ib/c-like\nfeatures (Ca-Ib/c objects) at peak light. Within the Ca-Ib/c events, we find two populations of events\ndistinguished by their red (g - r ≈ 1.5 mag) or green (g - r ≈ 0.5 mag) spectral colors at r-band peak.\nRed Ca-Ib/c events are characterized by strongly line-blanketed spectra, systematically slower light\ncurves, weaker and slower (by ≈ 3000 km s⁻¹) He lines and lower [Ca II]/[O I] flux ratio (by a factor\nof ≈ 2) in the nebular phase compared to the green Ca-Ib/c objects. Ca-Ia objects show typically\nmore luminous light curves (M_r ≈ -16.9 mag at peak) than Ca-Ib/c objects, strong line blanketing\nsignatures with intermediate red colors (g - r ≈ 1 mag at r-band peak), slow light curves, and weak\nor no [O I] in the nebular phase. Together, we find that the continuum of spectroscopic properties\nand the correlations thereof, the volumetric rates and striking old environments of these events are\nconsistent with progenitor channels involving the explosive burning of He shells on low mass white\ndwarfs over a range of shell and core masses. We posit that the Ca-Ia and red Ca-Ib/c objects are\nbroadly consistent with scenarios invoking the double detonation of He shells on white dwarfs with\nhigh He burning efficiency, while green Ca-Ib/c objects could arise from He shell explosions with lower\nHe burning efficiency such as detonations in lower density He shells or He shell deflagrations.\n", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/102522, title ="Progenitor, Precursor and Evolution of the Dusty Remnant of the Stellar Merger M31-LRN-2015", author = "Blagorodnova, N. and Karambelkar, V.", journal = "arXiv", month = "April", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200414-082207828", note = "© 2020 The Authors. \n\nLast updated 13 April 2020; in original form 13 April 2020. \n\nN. B. would like to thank O. Pejcha and M. MacLeod for useful discussions, A. Kurtenkov and S. C. Williams for making available the spectra of M31-LRN-2015, A. Pastorello for data on AT2017fjs, and T. Kaminski for the spectrum of V1309Sco. To M. Fraser, D. Perley, and R. M. Wagner for observations and data reduction, and to T. Szalai for the dust emission models. This work is part of the research programme VENI, with project number 016.192.277, which is (partly) financed by the Netherlands Organisation for Scientific Research (NWO). SK acknowledges the financial support of the Polish National Science Center (NCN) through the OPUS grant 2018/31/B/ST9/00334. P.E.N. acknowledges support from the DOE under grant DEAC02-05CH11231, Analytical Modeling for Extreme-Scale Computing Environments. CSK is supported by NSF grants AST-1908570 and AST-1814440. The Intermediate Palomar Transient Factory project is a scientific collaboration among the California Institute of Technology, Los Alamos National Laboratory, the\nUniversity of Wisconsin, Milwaukee, the Oskar Klein Center, the\nWeizmann Institute of Science, the TANGO Program of the University System of Taiwan, and the Kavli Institute for the Physics and Mathematics of the Universe. The WHT spectrum was taken under program (2014B/P29). This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. \n\nSome of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This work is based in part on observations made with the Large Binocular Telescope. The LBT is an international collaboration among institutions in the United States, Italy and Germany. The LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsge-sellschaft, Germany, representing the Max Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University; The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota and University of Virginia. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. We acknowledge Telescope Access Program (TAP) funded by the NAOC, CAS, and the Special Fund for Astronomy from the Ministry of Finance. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. This research made use of Astropy,4 a community-developed core Python package for Astronomy (Astropy Collaboration et al. 2013, 2018).", revision_no = "9", abstract = "M31-2015-LRN is a likely stellar merger discovered in the Andromeda Galaxy in 2015. We present new optical to mid-infrared photometry and optical spectroscopy for this event. The transient brightened by ∼3 mag as compared to its progenitor. The complex precursor emission, which started ∼2 years before the nova event, may be explained by the binary undergoing Roche-lobe overflow. The dynamical mass loss from the outer Lagrange point L2 creates an optically thick outflow to power the observed brightening of the system. We find two possible periods of 16±0.3 and 28.1±1.4 days at different phases of the precursor lightcurve, possibly related to the geometry of the mass-loss from the binary. Although the progenitor spectral energy distribution shows no evidence of pre-existing warm dust in system, the remnant forms an optically thick dust shell 2−4 months after the outburst peak. The optical depth of the shell increases after 1.5 years, suggesting the existence of shocks that enhance the dust formation process. We propose that the merger remnant is likely an inflated giant obscured by a cooling shell of gas with mass ∼0.2 M⊙ ejected at the onset of the common envelope phase.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/102525, title ="Towards An Integrated Optical Transient Utility", author = "Kulkarni, S. R.", journal = "arXiv", month = "April", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200414-093156733", note = "The principal survey that the Rubin Observatory will carry out\nis the Legacy Survey of Space and Time Survey or LSST. \n\nThis paper formed the basis of a talk I gave at the IAU-Kavli meeting \"Transients 2020\" (Capetown, February 3-8, 2020). As usual I am grateful to librarians and curators who maintain the databases that modern astronomy relies heavily. For this paper I single out ADS and TNS. \n\nI am most grateful to Ofer Yaron for providing insight into TNS; Evan Kirby, PI for NGPS, for discussions on throughputs of various spectrometers; and Christoffer Fremling for supplying me estimated annual SN discovery rates. I thank Jesper Sollerman, Anna Ho, Steve Schulze and Mickael Rigault for careful reading. Finally, I am grateful to the following for discussion or critical feedback or both: Ilaria Caiazzo, Richard Dekany, Avishay Gal-Yam, Paul Groot, Matthew Graham, Thomas Matheson, Jakob Nordin, Eran Ofek, Daniel Perley, Robert Quimby, Armin Rest, Stephen Smartt and Jason Spyromilio. SRK thanks the Heising-Simons Foundation for supporting his research in time domain astronomy.", revision_no = "11", abstract = "The ongoing optical time-domain astronomy surveys are routinely reporting fifty transient candidates per night. Here, I investigate the demographics of astronomical transients and supernova classifications reported to the Transient Name Server in the year 2019. I find that only a tenth of the transients were spectrally classified. This severe \"bottleneck\" problem should concern astronomers and also funding agencies. The bottleneck will get worse by a factor of 20 (or more) once LSST comes on line. We need to fundamentally rethink the purpose of surveys for transients. Here, after undertaking a detailed investigation of this issue I offer some solutions. Going forward, astronomers will employ two different methodologies: (1) multi-band photometric method which is well suited to the study of very large, many tens of thousands, samples of faint transients; (2) spectral classifications of thousands of bright transients found in shallow and nightly cadenced wide-field photometry surveys and transients associated with galaxies in the local Universe. The latter program, in addition to unearthing new types of transients and offering astronomers opportunities to undertake extensive follow up of interesting transients, is needed to set the stage for the former. Specifically, I suggest a globally coordinated effort to spectrally classify a complete sample of bright supernovae (< ~19.5 mag) and transients within the local Universe (< 200 Mpc) The proposed program is within reach -- thanks to the on-going wide-field surveys, the development of novel spectrographs tuned for classification, great improvements in throughput of spectrographs and the increasing availability of robotic telescopes.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/104103, title ="Effects of Different Cosmic Ray Transport Models on Galaxy Formation", author = "Hopkins, Philip F. and Chan, T. K.", journal = "arXiv", month = "April", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200626-150130701", note = "Support for PFH was provided by NSF Collaborative Research\nGrants 1715847 & 1911233, NSF CAREER grant 1455342, and NASA grants 80NSSC18K0562 and JPL 1589742. CAFG was supported by NSF 1517491, 1715216, and CAREER 1652522; NASA 17-ATP17-0067; and by a Cottrell Scholar Award. Support for JS was provided by Rutherford Discovery Fellowship RDF-U001804 and Marsden Fund grant UOO1727 from the Royal Society Te Apārangi. DK was supported by NSF grant AST-1715101 and the Cottrell Scholar Award from the Research Corporation for Science Advancement. Numerical calculations were run on the Caltech compute cluster “Wheeler,” allocations FTA-Hopkins supported by the NSF and TACC, and NASA HEC SMD-16-7592.", revision_no = "24", abstract = "Cosmic rays (CRs) with ~GeV energies can contribute significantly to the energy and pressure budget in the interstellar, circumgalactic, and intergalactic medium (ISM, CGM, IGM). Recent cosmological simulations have begun to explore these effects, but almost all studies have been restricted to simplified models with constant CR diffusivity and/or streaming speeds. Physical models of CR propagation/scattering via extrinsic turbulence and self-excited waves predict transport coefficients which are complicated functions of local plasma properties. In a companion paper, we consider a wide range of observational constraints to identify proposed physically-motivated cosmic-ray propagation scalings which satisfy both detailed Milky Way (MW) and extra-galactic γ-ray constraints. Here, we compare the effects of these models relative to simpler 'diffusion+streaming' models on galaxy and CGM properties at dwarf through MW mass scales. The physical models predict large local variations in CR diffusivity, with median diffusivity increasing with galacto-centric radii and decreasing with galaxy mass and redshift. These effects lead to a more rapid dropoff of CR energy density in the CGM (compared to simpler models), in turn producing weaker effects of CRs on galaxy star formation rates (SFRs), CGM absorption profiles and galactic outflows. The predictions of the more physical CR models tend to lie 'in between' models which ignore CRs entirely and models which treat CRs with constant diffusivity.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/104104, title ="No missing photons for reionization: moderate ionizing photon escape fractions from the FIRE-2 simulations", author = "Ma, Xiangcheng and Quataert, Eliot", journal = "arXiv", month = "March", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200626-150134129", note = "The simulations and post-processing calculations used in this paper were run on XSEDE computational resources (allocations TG-AST120025, TG-AST130039, TG-AST140023, TG-AST140064, and TG-AST190028). This work was supported in part by a Simons Investigator Award from the Simons Foundation (EQ) and by NSF grant AST-1715070. AW was supported by NASA, through ATP grant 80NSSC18K1097 and HST grants GO-14734 and AR-15057 from STScI. PFH was supported by an Alfred P. Sloan Research Fellowship, NASA ATP Grant NNX14AH35G, and NSF Collaborative Research Grant #1411920 and CAREER grant #1455342. CAFG was supported by NSF through grants AST-1517491,¢aAST-1715216, and CAREER award AST-1652522, by NASA through grant¢a17-ATP17-0067,¢aand by a Cottrell Scholar Award from the Research Corporation for Science Advancement. DK was supported by NSF grant AST-1715101 and the Cottrell Scholar Award from the Research Corporation for Science Advancement.", revision_no = "13", abstract = "We present the escape fraction of hydrogen ionizing photons (f_(esc)) from a sample of 34 high-resolution cosmological zoom-in simulations of galaxies at z > 5 in the Feedback in Realistic Environments project, post-processed with a Monte Carlo radiative transfer code for ionizing radiation. Our sample consists of 8500 halos in M_(vir) ~ 10⁸--10¹² M_⊙ (M_★ ~ 10⁴--10¹⁰ M_⊙) at z = 5--12. We find the sample average increases with halo mass for M_(vir) ~ 10⁸--10^(9.5) M_sun, becomes nearly constant for M_vir~10^{9.5}--10^{11} M_⊙, and decreases at M_(vir) > 10¹¹ M_⊙. Equivalently, increases with stellar mass up to M_star~10^8 M_sun and decreases at higher masses. Even applying single-star stellar population synthesis models, we find a moderate ~0.2 for galaxies at M_★ ~ 10⁸ M_⊙. Nearly half of the escaped ionizing photons come from stars 1--3 Myr old and the rest from stars 3--10 Myr old. Binaries only have a modest effect, boosting by ~25--35% and the number of escaped photons by 60--80%. Most leaked ionizing photons are from vigorously star-forming regions that usually contain a feedback-driven kpc-scale superbubble surrounded by a dense shell. The shell is forming stars while accelerated, so new stars formed earlier in the shell are already inside the shell. Young stars in the bubble and near the edge of the shell can fully ionize some low-column-density paths pre-cleared by feedback, allowing a large fraction of their ionizing photons to escape. The decrease of at the high-mass end is due to dust attenuation, while at the low-mass end, decreases owing to inefficient star formation (and hence feedback). At fixed mass, tends to increase with redshift. Our simulations produce sufficient ionizing photons for cosmic reionization.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/102519, title ="DECam-GROWTH Search for the Faint and Distant Binary Neutron Star and Neutron Star-Black Hole Mergers in O3a", author = "Anand, Shreya and Andreoni, Igor", journal = "arXiv", month = "March", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200414-074207930", note = "This work was supported by the GROWTH project funded by the National Science Foundation under Grant No 1545949.", revision_no = "9", abstract = "Synoptic searches for the optical counterpart to a binary neutron star (BNS) or neutron star-black hole (NSBH) merger can pose significant challenges towards the discovery of kilonovae and performing multi-messenger science. In this work, we describe the advantage of a global multi-telescope network towards this end, with a particular focus on the key and complementary role the Dark Energy Camera (DECam) plays in multi-facility follow-up. We describe the Global Relay of Observatories Watching Transients Happen (GROWTH) Target-of-Opportunity (ToO) Marshal, a common web application we built to ingest events, plan observations, search for transient candidates, and retrieve performance summary statistics for all of the telescopes in our network. Our infrastructure enabled us to conduct observations of two events during O3a, S190426c and S190510g. Furthermore, our analysis of deep DECam observations of S190814bv conducted by the DESGW team, and access to a variety of global follow-up facilities allowed us to place meaningful constraints on the parameters of the kilonova and the merging binary. We emphasize the importance of a global telescope network in conjunction with a power telescope like DECam in performing searches for the counterparts to gravitational-wave sources.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/101796, title ="Physical models of streaming instabilities in protoplanetary disks", author = "Squire, Jonathan and Hopkins, Philip F.", journal = "arXiv", month = "March", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200309-151230451", note = "We thank P. Benítez-Llambay, J. Goodman, L. Krapp, and M. Pessah, for helpful discussions. Support for JS was provided by Rutherford Discovery Fellowship RDF-U001804 and Marsden Fund grant UOO1727, which are managed through the Royal Society Te Apārangi. Support for PFH was provided by NSF Collaborative Research Grants 1715847 & 1911233, NSF CAREER grant 1455342, and NASA grants 80NSSC18K0562 and JPL 1589742.", revision_no = "9", abstract = "We develop simple, physically motivated models for drag-induced dust-gas streaming instabilities, which are thought to be crucial for clumping grains to form planetesimals in protoplanetary disks. The models explain, based on the physics of gaseous epicyclic motion and dust-gas drag forces, the most important features of the streaming instability and its simple generalisation, the disk settling instability. Some of the key properties explained by our models include the sudden change in the growth rate of the streaming instability when the dust-to-gas-mass ratio surpasses one, the slow growth rate of the streaming instability compared to the settling instability for smaller grains, and the main physical processes underlying the growth of the most unstable modes in different regimes. As well as providing helpful simplified pictures for understanding the operation of an interesting and fundamental astrophysical fluid instability, our models may prove useful for analysing simulations and developing nonlinear theories of planetesimal growth in disks.", } @misc {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/102966, title ="Direct Multipixel Imaging and Spectroscopy of an Exoplanet with a Solar Gravity Lens Mission", author = "Turyshev, Slava G. and Shao, Michael", journal = "arXiv", month = "February", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200501-110449071", note = "We would like to express our gratitude to our many colleagues who have either collaborated with us on this report or given us their wisdom. We specifically thank Roy Nakagawa, Nathan Strange, Phil A. Willems, John L. West, Stacy Weinstein-Weiss, who provided us with very valuable comments, encouragement, support and stimulating discussions while this report was in preparation. \n\nWe acknowledge fruitful collaborations with several our NIAC Fellows, especially with Stephanie Thomas, John Brophy, Philip Lubin, Robert Adams and Nickolas Solomey. \n\nSeveral on-going collaborations with our industry partners, non-profit and academia contributed to our work, namely with NXTRAC, Explore, L’Garde, Firefly, Morpheus Space, Zeno Power Systems, Breakthrough StarShot, Space Venture Coalition, Texas A&M University, UCLA, Cornell Tech, MIT, University of Colorado in Colorado Springs, as well as NASA Ames Research Center, NASA Marshall Space Flight Center, and others.\nFinally, we are especially thankful to NASA Innovative Advanced Concepts (NIAC) for their support for our work in the pursuit of an exciting objective – using the SGL for direct high-resolution imaging and spectroscopy of a potentially habitable exoplanet. \n\nThe work described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. ©2020. All rights reserved. \n\nDisclaimer: The cost information contained in this document is of a budgetary and planning nature and is intended for informational purposes only. It does not constitute a commitment on the part of JPL and/or Caltech.", revision_no = "8", abstract = "We examined the solar gravitational lens (SGL) as the means to produce direct high-resolution, multipixel images of exoplanets. The properties of the SGL are remarkable: it offers maximum light amplification of ~1e11 and angular resolution of ~1e-10 arcsec. A probe with a 1-m telescope in the SGL focal region can image an exoplanet at 30 pc with 10-kilometer resolution on its surface, sufficient to observe seasonal changes, oceans, continents, surface topography. We reached and exceeded all objectives set for our study: We developed a new wave-optical approach to study the imaging of exoplanets while treating them as extended, resolved, faint sources at large but finite distances. We properly accounted for the solar corona brightness. We developed deconvolution algorithms and demonstrated the feasibility of high-quality image reconstruction under realistic conditions. We have proven that multipixel imaging and spectroscopy of exoplanets with the SGL are feasible. We have developed a new mission concept that delivers an array of optical telescopes to the SGL focal region relying on three innovations: i) a new way to enable direct exoplanet imaging, ii) use of smallsats solar sails fast transit through the solar system and beyond, iii) an open architecture to take advantage of swarm technology. This approach enables entirely new missions, providing a great leap in capabilities for NASA and the greater aerospace community. Our results are encouraging as they lead to a realistic design for a mission that will be able to make direct resolved images of exoplanets in our stellar neighborhood. It could allow exploration of exoplanets relying on the SGL capabilities decades, if not centuries, earlier than possible with other extant technologies. The architecture and mission concepts for a mission to the strong interference region of the SGL are promising and should be explored further.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/101798, title ="Testing Physical Models for Cosmic Ray Transport Coefficients on Galactic Scales: Self-Confinement and Extrinsic Turbulence at GeV Energies", author = "Hopkins, Philip F. and Squire, Jonathan", journal = "arXiv", month = "February", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200309-153702109", note = "Support for PFH was provided by NSF Collaborative Research Grants 1715847 & 1911233, NSF CAREER grant 1455342, and NASA grants 80NSSC18K0562 and JPL 1589742. CAFG was supported by NSF 1517491, 1715216, and CAREER 1652522; NASA 17-ATP17-0067; and by a Cottrell Scholar Award. DK was supported by NSF grant AST-1715101 and the Cottrell Scholar Award. Numerical calculations were run on the Caltech compute cluster “Wheeler,” allocations from XSEDE TG-AST130039 and PRAC NSF.1455342 supported by the NSF, and NASA HEC SMD-16-7592. Data used in this work were hosted on facilities supported by the Scientific Computing Core at the Flatiron Institute, a division of the Simons Foundation.", revision_no = "11", abstract = "The microphysics of ~GeV cosmic ray (CR) transport on galactic scales remain deeply uncertain, with almost all studies adopting simple prescriptions (e.g. constant-diffusivity). We explore different physically-motivated, anisotropic, dynamical CR transport scalings in high-resolution cosmological FIRE simulations of dwarf and ~L∗ galaxies where scattering rates vary with local plasma properties motivated by extrinsic turbulence (ET) or self-confinement (SC) scenarios, with varying assumptions about e.g. turbulent power spectra on un-resolved scales, Alfven-wave damping, etc. We self-consistently predict observables including γ-rays (L_γ), grammage, residence times, and CR energy densities to constrain the models. We demonstrate many non-linear dynamical effects (not captured in simpler models) tend to enhance confinement. For example, in multi-phase media, even allowing arbitrary fast transport in neutral gas does not substantially reduce CR residence times (or L_γ), as transport is rate-limited by the ionized WIM and 'inner CGM' gaseous halo (10⁴−10⁶ K gas within 10-30 kpc), and L_γ can be dominated by trapping in small 'patches.' Most physical ET models contribute negligible scattering of ~1-10 GeV CRs, but it is crucial to account for anisotropy and damping (especially of fast modes) or else scattering rates would violate observations. We show that the most widely-assumed scalings for SC models produce excessive confinement by factors >100 in the WIM and inner CGM, where turbulent and Landau damping dominate. This suggests either a breakdown of quasi-linear theory used to derive the CR transport parameters in SC, or that other novel damping mechanisms dominate in intermediate-density ionized gas.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/101810, title ="Cosmic-Ray Driven Outflows to Mpc Scales from L∗ Galaxies", author = "Hopkins, Philip F. and Chan, T. K.", journal = "arXiv", month = "February", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200310-082303427", note = "Support for PFH and co-authors was provided by an Alfred P. Sloan Research Fellowship, NSF Collaborative Research Grant #1715847 and CAREER grant #1455342, and NASA grants NNX15AT06G, JPL 1589742, 17-ATP17-0214. CAFG was supported by NSF through grants AST-1517491, AST-1715216, and CAREER award AST-1652522, by NASA through grant 17-ATP17-0067, by STScI through grants HST-GO-14681.011, HST-GO-14268.022-A, and HST-AR-14293.001-A, and by a Cottrell Scholar Award from the Research Corporation for Science Advancement. DK was supported by NSF grant AST-1715101 and the Cottrell Scholar Award from the Research Corporation for Science Advancement. Numerical calculations were run on the Caltech compute cluster “Wheeler,” allocations FTA-Hopkins supported by the NSF and TACC, and NASA HEC SMD-16-7592.", revision_no = "11", abstract = "We study the effects of cosmic rays (CRs) on outflows from star-forming galaxies in the circum and inter-galactic medium (CGM/IGM), in high-resolution, fully-cosmological FIRE-2 simulations (accounting for mechanical and radiative stellar feedback, magnetic fields, anisotropic conduction/viscosity/CR diffusion and streaming, and CR losses). We showed previously that massive (M_(halo) ≳ 10¹¹ M_⊙), low-redshift (z ≲ 1−2) halos can have CR pressure dominate over thermal CGM pressure and balance gravity, giving rise to a cooler CGM with an equilibrium density profile. This dramatically alters outflows. Absent CRs, high gas thermal pressure in massive halos \"traps\" galactic outflows near the disk, so they recycle. With CRs injected in supernovae as modeled here, the low-pressure halo allows \"escape\" and CR pressure gradients continuously accelerate this material well into the IGM in \"fast\" outflows, while lower-density gas at large radii is accelerated in-situ into \"slow\" outflows that extend to >Mpc scales. CGM/IGM outflow morphologies are radically altered: they become mostly volume-filling (with inflow in a thin mid-plane layer) and coherently biconical from the disk to >Mpc. The CR-driven outflows are primarily cool (T∼10⁵ K) and low-velocity. All of these effects weaken and eventually vanish at lower halo masses (≲ 10¹¹ M_⊙) or higher redshifts (z ≳ 1−2), reflecting the ratio of CR to thermal+gravitational pressure in the outer halo. We present a simple analytic model which explains all of the above phenomena.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/101895, title ="Thermal Kinetic Inductance Detectors for Millimeter-Wave Astrophysics", author = "Wandui, A. and Bock, J. J.", journal = "arXiv", month = "January", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200312-132341532", note = "The research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the NationalAeronautics and Space Administration. We thank the JPL Research and Technology Development (RTD) program for supporting funds, as well as the Dominic Orr Graduate Fellowship in Physics at Caltech for supporting Mr. Wandui’s graduate research.", revision_no = "8", abstract = "Thermal Kinetic Inductance Detectors (TKIDs) combine the excellent noise performance of traditional bolometers with a radio frequency (RF) multiplexing architecture that enables the large detector counts needed for the next generation of millimeter-wave instruments. Here we present dark prototype TKID pixels that demonstrate a noise equivalent power NEP = 2×10⁻¹⁷√W/Hz with a 1/f knee at 0.1 Hz, suitable for background-limited noise performance at 150 GHz from a ground-based site. We discuss the optimizations in the device design and fabrication techniques to realize optimal electrical performance and high quality factors at a bath temperature of 250 mK.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/101813, title ="Reproducing the CO-to-H₂ conversion factor in cosmological simulations of Milky Way-mass galaxies", author = "Keating, Laura C. and Richings, Alexander J.", journal = "arXiv", month = "January", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200310-084830640", note = "© 2019 The Authors. \n\nWe thank Desika Narayanan and Xiangcheng Ma for their comments on this draft. LCK acknowledges the support of a CITA fellowship. We acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC). This research was undertaken, in part, because of funding from the Canada Research Chairs program. CAFG was supported by NSF through grants AST-1517491, AST-1715216, and CAREER award AST-1652522; by NASA through grant 17-ATP17-0067; and by a Cottrell Scholar Award from the Research Corporation for Science Advancement. Support for PFH was provided by an Alfred P. Sloan Research Fellowship, NSF Collaborative Research Grant 1715847 and CAREER grant 1455342, and NASA grants NNX15AT06G, JPL 1589742, 17-ATP17-0214. AW received support from NASA, through ATP grant 80NSSC18K1097 and HST grants GO-14734 and AR-15057 from STScI, the Heising-Simons Foundation, and a Hellman Fellowship. DK was supported by NSF grant AST-1715101 and the Cottrell Scholar Award from the Research Corporation for Science Advancement. RF acknowledges financial support from the Swiss National Science Foundation (grant no 157591). Support for SRL was provided by NASA through Hubble Fellowship grant HST-JF2-51395.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. Computations were performed on the Niagara supercomputer at the SciNet HPC Consortium. SciNet is funded by: the Canada Foundation for Innovation; the Government of Ontario; Ontario Research Fund - Research Excellence; and the University of Toronto (Ponce et al. 2019; Loken et al. 2010).", revision_no = "13", abstract = "We present models of CO(1-0) emission from Milky Way-mass galaxies at redshift zero in the FIRE-2 cosmological zoom-in simulations. We calculate the molecular abundances by post-processing the simulations with an equilibrium chemistry solver while accounting for the effects of local sources, and determine the emergent CO(1-0) emission using a line radiative transfer code. We find that the results depend strongly on the shielding length assumed, which in our models sets the attenuation of the incident UV radiation field. Commonly used choices for the shielding length, such as the Jeans length, result in CO abundances that are too high at a given H₂ abundance. We find that a model with a distribution of shielding lengths, which has a median shielding length of ∼3 pc in cold gas (T<300 K) for both CO and H₂, is able to reproduce both the observed CO(1-0) luminosity and inferred CO-to-H₂ conversion factor at a given star formation rate compared with observations. We suggest that this short shielding length can be thought of as a subgrid model which controls the amount of radiation that penetrates giant molecular clouds.", } @misc {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/101852, title ="The Habitable Exoplanet Observatory (HabEx) Mission Concept Study Final Report", author = "Gaudi, B. Scott and Seager, Sara", journal = "arXiv", month = "January", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200311-111308399", note = "© 2019. All rights reserved. \n\nHabitable Exoplanet Observatory Final Report. \n\nThe HabEx Study Team would like to thank the following for their efforts in supporting the development of the HabEx Report: Technical reviewers, for their dedication and feedback: Randall Bartman, David Bearden, Charles Beichman, Ruslan Belikov, Andrew Coffey, Alyssa Deardroff, Alan Didion, Benji Donitz, Aigneis Frey, Anthony Freeman, Todd Gaier, Gregory Garner, Paul Graf, Ravi Kumar Kopparapu, Amanda la Venture, Roger Lee, Elizabeth Luthman, Charley Noecker, Jane Rigby, Hari Subedi, Mark Swain, Neil Zimmerman, and Steven Zusack. \n\nMembers of the Independent Cost Estimate and Independent Schedule Assessment Team, for their independent assessment: Fred Doumani, Erica Beam, and Jerry Shen Everyone involved in unlimited release review, for ability to meet our schedule needs: Alex Abramovici, Amanda Beckett, Douglas Isbell, Peter Kahn, Young Lee, Kathleen Lynn, Sunjay Moorthay, and Danette Zuniga. \n\nAki Roberge (NASA Goddard Space Flight Center) for her unflagging efforts to promote cooperation and collaboration between the LUVOIR and HabEx study teams. \n\nDisclaimer: Pre-Decisional Information – For Planning and Discussion Purposes Only This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. \n\nThe cost information contained in this document is of a budgetary and planning nature and is intended for informational purposes only. It does not constitute a commitment on the part of JPL and Caltech.", revision_no = "9", abstract = "The Habitable Exoplanet Observatory, or HabEx, has been designed to be the Great Observatory of the 2030s. For the first time in human history, technologies have matured sufficiently to enable an affordable space-based telescope mission capable of discovering and characterizing Earthlike planets orbiting nearby bright sunlike stars in order to search for signs of habitability and biosignatures. Such a mission can also be equipped with instrumentation that will enable broad and exciting general astrophysics and planetary science not possible from current or planned facilities. HabEx is a space telescope with unique imaging and multi-object spectroscopic capabilities at wavelengths ranging from ultraviolet (UV) to near-IR. These capabilities allow for a broad suite of compelling science that cuts across the entire NASA astrophysics portfolio. HabEx has three primary science goals: (1) Seek out nearby worlds and explore their habitability; (2) Map out nearby planetary systems and understand the diversity of the worlds they contain; (3) Enable new explorations of astrophysical systems from our own solar system to external galaxies by extending our reach in the UV through near-IR. This Great Observatory science will be selected through a competed GO program, and will account for about 50% of the HabEx primary mission. The preferred HabEx architecture is a 4m, monolithic, off-axis telescope that is diffraction-limited at 0.4 microns and is in an L2 orbit. HabEx employs two starlight suppression systems: a coronagraph and a starshade, each with their own dedicated instrument.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/102520, title ="Seventeen Tidal Disruption Events from the First Half of ZTF Survey Observations: Entering a New Era of Population Studies", author = "van Velzen, Sjoert and Gezari, Suvi", journal = "arXiv", month = "January", year = "2020", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200414-075012273", note = "Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. SED Machine is based upon work supported by the National Science Foundation under Grant No. 1106171. \n\nThese results made use of the Discovery Channel Telescope at Lowell Observatory. Lowell is a private, non-profit institution dedicated to astrophysical research and public appreciation of astronomy and operates the DCT in partnership with Boston University, the University of Maryland, the University of Toledo, Northern Arizona University and Yale University. The upgrade of the DeVeny optical spectrograph has been funded by a generous grant from John and Ginger Giovale. The W. M. Keck Observatory is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA; the Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council. Research at Lick Observatory is partially supported by a generous gift from Google. \n\nWe thank the Swift team, including the Observation Duty Scientists, and the science planners for promptly approving and executing our Swift observations. We also acknowledge the use of public data from the Swift data archive. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. We thank J. Brown and M. Siebert for help with Keck observations. \n\nS. van Velzen is supported by the James Arhtur Fellowship. S. Gezari is supported in part by NSF CAREER grant 1454816 and NSF AAG grant 1616566. \n\nN.R. acknowledges the support of a Joint Space-Science Institute prize postdoctoral fellowship. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 759194 - USNAC). A.Y.Q.H. is supported by a National Science Foundation Graduate Research Fellowship under Grant No. DGE1144469. This work was supported by the GROWTH project funded by the National Science Foundation under PIRE Grant No. 1545949. C. Fremling gratefully acknowledges support of his research by the Heising-Simons Foundation (#2018-0907). The UCSC transient team is supported in part by NSF grant AST-1518052, NASA/Swift grant 80NSSC19K1386, the Gordon & Betty Moore Foundation, the Heising-Simons Foundation, and by a fellowship from the David and Lucile Packard Foundation to R.J.F. \n\nSoftware: Ampel (Nordin et al. 2019), Astropy (Astropy Collaboration et al. 2018), catsHTM(Soumagnac & Ofek 2018b),emcee(Foreman-Mackey et al. 2013), extcats (github.com/MatteoGiomi/extcats), gPhoton (Million et al. 2016), HEAsoft (Arnaud 1996), FSPS (Conroy et al. 2009; Conroy & Gunn 2010;Foreman-Mackey et al. 2014), Prospector (Johnson & Leja 2017).", revision_no = "15", abstract = "While tidal disruption events (TDEs) have long been heralded as laboratories for the study of quiescent black holes, the small number of known TDEs and uncertainties in their emission mechanism have hindered progress towards this promise. Here present 17 new TDEs that have been detected recently by the Zwicky Transient Facility along with Swift UV and X-ray follow-up observations. Our homogeneous analysis of the optical/UV light curves, including 22 previously known TDEs from the literature, reveals a clean separation of light curve properties with spectroscopic class. The TDEs with Bowen fluorescence features in their optical spectra have smaller blackbody radii, as well as longer rise times and higher disruption rates compared to the rest of the sample. The Bowen fluorescence mechanism requires a high density which can be reached at smaller radii, which in turn yields longer diffusion timescales. Thus, the difference in rise times suggests the pre-peak TDE light curves are governed not by the fallback timescale, but instead by the diffusion of photons through the tidal debris. The small subset of TDEs that show only helium emission lines in their spectra have the longest rise times, the highest luminosities and the lowest rates. We also report, for the first time, the detection of soft X-ray flares from a TDE on day timescales. Based on the fact the flares peak at a luminosity similar to the optical/UV blackbody luminosity, we attribute them to brief glimpses through a reprocessing layer that otherwise obscures the inner accretion flow.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/102518, title ="Gaia GraL: Gaia DR2 Gravitational Lens Systems. V. Doubly-imaged QSOs discovered from entropy and wavelets", author = "Krone-Martins, A. and Graham, M. J.", journal = "arXiv", month = "December", year = "2019", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200414-072917417", note = "Received December 20, 2019. \n\nSome of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Partially based on observations collected at the European Southern Observatory, Chile (104.A-0575). \n\nAKM acknowledges the support from the Portuguese Fundação para a Ciência e a Tecnologia (FCT) through grants SFRH/BPD/74697/2010, PTDC/FIS-AST/31546/2017, from the Portuguese Strategic Programme UID/FIS/00099/2013 for CENTRA, from the ESA contract AO/1-7836/14/NL/HB and from the Caltech Division of Physics, Mathematics and Astronomy for hosting research leaves during 2017-2018 and 2019, when the ideas and the codes underlying this work were initially developed. MJG, SGD and AJD acknowledge a partial support from the NSF grants AST-1413600, AST-1518308, AST-1815034, and the NASA grant 16-ADAP16-0232. AMN acknowledges support from the NASA Postdoctoral Program Fellowship. The work of DS and AMN were carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. LD acknowledges support from the ESA PRODEX Programme ‘Gaia-DPAC QSOs’ and from the Belgian Federal Science Policy Office. \n\nOW was supported by the Humboldt Research Fellowship for Postdoctoral Researchers. DD is supported by an Australian Government Research Training Program Scholarship. TM acknowledges the support of the Australian Research Council through grant FT150100099. We acknowledge partial support from ‘Actions sur projet INSU-PNGRAM’, and from the Brazil-France exchange programmes Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) – Comité Français d’Évaluation de la Coopération Universitaire et Scientifique avec le Brésil (COFECUB). This work has made use of the computing facilities of the Laboratory of Astroinformatics (IAG/USP, NAT/Unicsul), whose purchase was made possible by the Brazilian agency FAPESP (grant 2009/54006-4) and the INCT-A, and we thank the entire LAi team, specially Carlos Paladini, Ulisses Manzo Castello, Luis Ricardo Manrique and Alex Carciofi for the support. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 787886). We thank Rick White from Space Telescope Science Institute for the support with the PS1DR2 images. The Pan-STARRS1 Surveys (PS1) and the PS1 public science archive have been made possible through contributions by the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, the Queen’s University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under Grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation Grant No. AST-1238877, the University of Maryland, Eotvos Lorand University (ELTE), the Los Alamos National Laboratory, and the Gordon and Betty Moore Foundation. The Dark Energy Camera Legacy Survey was conducted at the Blanco telescope, Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory (NOAO) (DECaLS; NOAO Proposal ID # 2014B-0404; PIs: David Schlegel and Arjun Dey). The Legacy Surveys project is honored to be permitted to conduct astronomical research on Iolkam Du’ag (Kitt Peak), a mountain with particular significance to the Tohono O’odham Nation. The Australia Telescope Compact Array is part of the Australia Telescope National Facility which is funded by the Australian Government for operation as a National Facility managed by CSIRO. This work has made use of results from the ESA space mission Gaia, the data from which were processed by the Gaia Data Processing and Analysis Consortium (DPAC). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. The Gaia mission website is: http://www.cosmos.esa.int/gaia. Some of the authors are members of the Gaia Data Processing and Analysis Consortium (DPAC).", revision_no = "14", abstract = "The discovery of multiply-imaged gravitationally lensed QSOs is fundamental to many astronomical and cosmological studies. However, these objects are rare and challenging to discover due to requirements of high-angular resolution astrometric, multiwavelength photometric and spectroscopic data. This has limited the number of known systems to a few hundred objects. We aim to reduce the constraints on angular resolution and discover multiply-imaged QSO candidates by using new candidate selection principles based on unresolved photometric time-series and ground-based images from public surveys. We selected candidates for multiply-imaged QSOs based on low levels of entropy computed from Catalina unresolved photometric time-series or Euclidean similarity to known lenses in a space defined by the wavelet power spectra of Pan-STARSS DR2 or DECaLS DR7 images, combined with multiple {\\it Gaia} DR2 sources or large astrometric errors and supervised and unsupervised learning methods. We then confirmed spectroscopically some candidates with the Palomar Hale, Keck-I, and ESO/NTT telescopes. Here we report the discovery and confirmation of seven doubly-imaged QSOs and one likely double quasar. This demonstrates the potential of combining space-astrometry, even if unresolved, with low spatial-resolution photometric time-series and/or low-spatial resolution multi-band imaging to discover multiply-imaged lensed QSOs.", } @misc {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/101786, title ="Astro2020 APC White Paper: Theoretical Astrophysics 2020-2030", author = "Kollmeier, Juna A. and Anderson, Lauren", journal = "arXiv", month = "December", year = "2019", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200309-124819106", revision_no = "10", abstract = "The past two decades have seen a tremendous investment in observational facilities that promise to reveal new and unprecedented discoveries about the universe. In comparison, the investment in theoretical work is completely dwarfed, even though theory plays a crucial role in the interpretation of these observations, predicting new types of phenomena, and informing observing strategies. In this white paper, we argue that in order to reach the promised critical breakthroughs in astrophysics over the next decade and well beyond, the national agencies must take a serious approach to investment in theoretical astrophysics research. We discuss the role of theory in shaping our understanding of the universe, and then we provide a multi-level strategy, from the grassroots to the national, to address the current underinvestment in theory relative to observational work.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/101780, title ="PlanetEvidence: Planet or Noise?", author = "Golomb, Jason and Rocha, Graça", journal = "arXiv", month = "December", year = "2019", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200309-112437574", note = "GR would like to acknowledge useful discussions with Jeff Jewell. The research presented here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.", revision_no = "8", abstract = "The work presented here attempts at answering the question: how do we decide when a given adetection is a planet or just residual noise in exoplanet direct imaging data? To this end we present a method implemented within a Bayesian framework: (1) to unify 'source detection', and, 'source characterization' into one single rigorous mathematical framework; (2) to enable an adequate hypothesis testing given the S/N of the data; (3) to enhance the detectability of planets faint signal in the presence of instrumental and background noise and to optimize the characterization of the planet. As a proof of concept we implemented a routine named ", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/102649, title ="Constraints on the binary black hole hypothesis for system LB-1", author = "Shen, Rong-Feng and Matzner, Christopher D.", journal = "arXiv", month = "November", year = "2019", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200420-103804380", note = "RFS thanks the hospitality of Canadian Institute of Theoretical Astrophysics where part of this work was carried out.", revision_no = "9", abstract = "At about 70 solar masses, the recently-discovered dark object orbited by a B-type star in the system LB-1 is difficult to understand as the end point of standard stellar evolution, except as a binary black hole (BBH). LB-1 shows a strong, broad H-alpha emission line that is best attributed to a gaseous disk surrounding the dark mass. We use the observed H-alpha line shape, particularly its wing extension, to constrain the inner radius of the disk and thereby the separation of a putative BBH. The hypothesis of a current BBH is effectively ruled out on the grounds that its merger time must be a small fraction of the current age of the B star. The hypothesis of a previous BBH that merged to create the current dark mass is also effectively ruled out by the low orbital eccentricity, due to the combination of mass loss and kick resulted from gravitational wave emission in any past merger. We conclude that the current dark mass is a single black hole produced by the highly mass-conserving, monolithic collapse of a massive star.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/100520, title ="Constraints on dark photons and axion-like particles from SuperCDMS Soudan", author = "Aralis, T. and Chang, Y.-Y.", month = "November", year = "2019", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200106-075205920", note = "The SuperCDMS collaboration gratefully acknowledges technical assistance from the staff of the Soudan Underground Laboratory and the Minnesota Department of Natural Resources. The iZIP detectors were fabricated in the Stanford Nanofabrication Facility, which is a member of the National Nanofabrication Infrastructure Network, sponsored and supported by the NSF. Funding and support were received from the National Science Foundation, the U.S. Department of Energy, Fermilab URA Visiting Scholar Grant No. 15-S-33, NSERC Canada, the Canada Excellence Research Chair Fund, the McDonald Institute (Canada), MultiDark (Spanish MINECO), and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - Project No. 420484612. The SuperCDMS collaboration prepared this document using the resources of the Fermi National Accelerator Laboratory (Fermilab), a U.S. Department of Energy, Office of Science, HEP User Facility. Fermilab is managed by Fermi Research Alliance, LLC (FRA), acting under Contract No. DE-AC02-07CH11359. Pacific Northwest National Laboratory is operated by Battelle Memorial Institute under Contract No. DE-AC05-76RL01830 for the U.S. Department of Energy. SLAC is operated under Contract No. DEAC02-76SF00515 with the U.S. Department of Energy.", revision_no = "11", abstract = "We present an analysis of electron recoils in cryogenic germanium detectors operated during the SuperCDMS Soudan experiment. The data are used to set new constraints on the axioelectric coupling of axion-like particles and the kinetic mixing parameter of dark photons, assuming the respective species constitutes all of the galactic dark matter. This study covers the mass range from 40 eV/c² to 500 eV/c² for both candidates, excluding previously untested parameter space for masses below ~1 keV/c². For the kinetic mixing of dark photons, values below 10⁻¹⁵ are reached for particle masses around 100 eV/c²; for the axioelectric coupling of axion-like particles, values below 10⁻¹² are reached for particles with masses in the range of a few-hundred eV/c².", } @misc {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/103734, title ="NASA Probe Study Report: Farside Array for Radio Science Investigations of the Dark ages and Exoplanets (FARSIDE)", author = "Burns, Jack O. and Hallinan, Gregg", journal = "arXiv", month = "November", year = "2019", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200605-134134203", note = "© 2019. \n\nNASA Probe final study report. \n\nPart of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. \n\nThe cost information contained in this document is of a budgetary and planning nature and is intended for informational purposes only. It does not constitute a commitment on the part of JPL and/or Caltech.", revision_no = "9", abstract = "This is the final report submitted to NASA for a Probe-class concept study of the \"Farside Array for Radio Science Investigations of the Dark ages and Exoplanets\" (FARSIDE), a low radio frequency interferometric array on the farside of the Moon. The design study focused on the instrument, a deployment rover, the lander and base station, and delivered an architecture broadly consistent with the requirements for a Probe mission. This notional architecture consists of 128 dipole antennas deployed across a 10 km area by a rover, and tethered to a base station for central processing, power and data transmission to the Lunar Gateway, or an alternative relay satellite. FARSIDE would provide the capability to image the entire sky each minute in 1400 channels spanning frequencies from 150 kHz to 40 MHz, extending down two orders of magnitude below bands accessible to ground-based radio astronomy. The lunar farside can simultaneously provide isolation from terrestrial radio frequency interference, auroral kilometric radiation, and plasma noise from the solar wind. This would enable near-continuous monitoring of the nearest stellar systems in the search for the radio signatures of coronal mass ejections and energetic particle events, and would also detect the magnetospheres for the nearest candidate habitable exoplanets. Simultaneously, FARSIDE would be used to characterize similar activity in our own solar system, from the Sun to the outer planets. Through precision calibration via an orbiting beacon, and exquisite foreground characterization, FARSIDE would also measure the Dark Ages global 21-cm signal at redshifts from 50-100. It will also be a pathfinder for a larger 21-cm power spectrum instrument by carefully measuring the foreground with high dynamic range.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/99946, title ="An extremely low-density and temperate giant exoplanet", author = "Santerne, A. and Dai, F.", month = "November", year = "2019", url = "https://resolver.caltech.edu/CaltechAUTHORS:20191120-083312061", note = "We are grateful to Mikkel Lund for sharing the manuscript on the asteroseismic constraints of HIP41378 before its publication. This has been extremely useful for the analyses presented here and to reach these results. The HARPS team is grateful to the HARPS observers who conducted part of the visitor-mode observations at La Silla Observatory: David Anderson, Nicola Astudillo, Xavier Bonfils, Romina Ibañez Bustos, David Ehrenreich, Melissa Hobson, Kristine Lam, Baptiste Lavie, Ester Linder, Felipe Murgas, Lorenzo Pino, Julia Seidel, & Aurélien Wyttenbach. \n\nBased on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 198.C-0169 and 0102.C-0171. Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Instituto Nazionale di Astrofísica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile. Based in part on observations made at Observatoire de Haute Provence (CNRS), France. This paper includes data collected by the K2 mission. Funding for the K2 mission is provided by the NASA Science Mission directorate. Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. \n\nThis publication makes use of The Data & Analysis Center for Exoplanets (DACE), which is a facility based at the University of Geneva (CH) dedicated to extrasolar planets data visualisation, exchange and analysis. DACE is a platform of the Swiss National Centre of Competence in Research (NCCR) PlanetS, federating the Swiss expertise in Exoplanet research. The DACE platform is available at https://dace.unige.ch. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This research has made use of the VizieR catalogue access tool, CDS, Strasbourg, France. The original description of the VizieR service was published in A&AS 143, 23. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/\nCalifornia Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for\nthe DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. \n\nThe French group acknowledges financial support from the French Programme National de Planétologie (PNP, INSU). The Porto group is supported by the Fundação para a Ciência e a Tecnologia (FCT) / MCTES through national funds (PIDDAC) and by FEDER - Fundo Europeu de Desenvolvimento Regional through COMPETE2020 - Programa Operacional Competitividade e Internacionalização by these grants: UID/FIS/04434/2019; PTDC/FIS-AST/32113/2017 & POCI-01-0145-FEDER-032113; PTDC/FIS-AST/28953/2017 & POCI-01-0145-FEDER-028953. VAd, SGS, EDM, SCCB acknowledge the support from through Investigador FCT contract nr. IF/00650/2015/CP1273/CT0001, IF/00028/2014/CP1215/CT0002, IF/00849/2015/CP1273/CT0003, IF/01312/2014/CP1215/CT0004 (respectively). \n\nSHo acknowledges support by the fellowships PD/BD/128119/2016 funded by FCT (Portugal). ODSD is supported in the form of work contract (DL 57/2016/CP1364/CT0004) funded by national funds through FCT. The Geneva group thanks the Swiss National Science Foundation (SNSF) and the Geneva University for their continuous support to the exoplanet researches. This work has been in particular carried out in the frame of the National Centre for Competence in Research PlanetS supported by SNSF. XDu is grateful to the Branco-Weiss Fellowship–Society in Science for its continuous support. This research has been funded by the Spanish State Research Agency (AEI) Projects No.ESP2017-87676-C5-1-R and No. MDM-2017-0737 Unidad de Excelencia “María de Maeztu” - Centro de Astrobiología (INTACSIC). DJA acknowledges support from the STFC via an Ernest Rutherford Fellowship (ST/R00384X/1).\nDB acknowledges support from an NSERC PGS-D scholarship. DJAB acknowledges support from the UK Space Agency (UKSA). DLP acknowledges support through a Royal Society Wolfson Merit Award. IJMC acknowledges support from the NSF through grant AST-1824644, and from NASA through Caltech/JPL grant RSA-1610091. MRK acknowledges support from the NSF Graduate Research Fellowship, grant No. DGE 1339067. MDa acknowledges financial support from Progetto Premiale 2015 FRONTIERA funding scheme of the Italian Ministry of Education, University, and Research. CDD acknowledges support from the K2 Guest Observer program (80NSSC18K0304 & 80NSSC19K0099) and the TESS Guest Investigator Program (80NSSC18K1583). Parts of this work have been supported by the National Aeronautics and Space\nAdministration under grant No. NNX17AB59G issued through the Exoplanets Research Program. LMa acknowledges support from PLATO ASI-INAF agreement n.2015-019-R.1-2018. AMo acknowledges support from Senior Kavli Institute Fellowships at the University of Cambridge. HPO acknowledges support from Centre National d’Etudes Spatiales (CNES) grant 131425-PLATO. JKT acknowledges that support for this work was provided by NASA through Hubble Fellowship grant HST-HF2-51399.001 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. AVa’s work was performed under contract with the California Institute of Technology / Jet Propulsion Laboratory funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. CAW would like to acknowledge support from UK Science Technology and Facility Council grant ST/P000312/1. PJW has been supported by STFC through consolidated grants ST/L000733/1 and ST/P000495/1. ACC acknowledges support from the Science and Technology Facilities Council (STFC) consolidated grant number ST/R000824/1 and UKSA grant ST/R003203/1. LMW acknowledges support from the Beatrice Watson Parrent Fellowship. JFD acknowledges funding from the European Research Council (ERC) under the H2020 research & innovation programme (grant agreement #740651 NewWorlds). \n\nThe authors declare that they have no competing financial interests. \n\nAuthors Contributions: ASa led the Analysis Task Force to which LMa, MRK, XDu, AVa, NCH, AMo, TAL are members and wrote the manuscript. CDD coordinated the observations from the radial-velocity instruments. HARPS programs CoIs and associated collaborators: VAd, ADJA, DBar, SCCB, DBay, IBo, ASB, FBo, DJAB, MRD, EDM, ODe, RFD, GH´e, PFi, SHo, JLB, TAL, CLo, OMo, LDN, HPO, DLP, ASa (PI), NCS, SGS, SUd, AVi, PJW. HARPS-N CoIs and associated collaborators: ASB, LAB, ACC, RCo, MDa, CDD, XDu, PFi, AGh, AHa, DWL, MLM (chair), CLo, LMa, AFMF, EMo, AMo, CNa, DFP, EPo, KRi, DS´e, ASo, SUd (chair), AVa, CAW. HIRES CoIs, major observers, and data reduction: CDD, MRK, DBe, IJMC (PI), BJF, LAH, AWH, HIs, EAP, ESi, LMW. PFS CoIs, builders, and data reduction: FDa, RPB, JDC, SAS, JKT, SXW, JNW. ESPaDOnS CoIs and data reduction: IBo, DBar, JFD, MRD, JLB, TAL, CMo, ASa (PI), NCS. \n\nData Availability Statement: The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.", revision_no = "18", abstract = "Transiting extrasolar planets are key objects in the study of the formation, migration, and evolution of planetary systems. In particular, the exploration of the atmospheres of giant planets, through transmission spectroscopy or direct imaging, has revealed a large diversity in their chemical composition and physical properties. Studying these giant planets allows one to test the global climate models that are used for the Earth and other solar system planets. However, these studies are mostly limited either to highly-irradiated transiting giant planets or directly-imaged giant planets at large separations. Here we report the physical characterisation of the planets in a bright multi-planetary system (HIP41378) in which the outer planet, HIP41378 f is a Saturn-sized planet (9.2 ± 0.1 R⊕) with an anomalously low density of 0.09 ± 0.02 g cm⁻³ that is not yet understood. Its equilibrium temperature is about 300 K. Therefore, it represents a planet with a mild temperature, in between the hot Jupiters and the colder giant planets of the Solar System. It opens a new window for atmospheric characterisation of giant exoplanets with a moderate irradiation, with the next-generation space telescopes such as JWST and ARIEL as well as the extremely-large ground-based telescopes. HIP41378 f is thus an important laboratory to understand the effect of the irradiation on the physical properties and chemical composition of the atmosphere of planets.", } @article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/101822, title ="Swirls of FIRE: Spatially Resolved Gas Velocity Dispersions and Star Formation Rates in FIRE-2 Disk Environments", author = "Orr, Matthew E. and Hayward, Christopher C.", journal = "arXiv", month = "October", year = "2019", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200310-104835304", note = "© 2019 The Authors. \n\nMEO is grateful for the encouragement of his late father, SRO, in studying astrophysics, and is supported by the National Science Foundation Graduate Research Fellowship under Grant No. 1144469. The Flatiron Institute is supported by the Simons Foundation. Support for AMM is provided by NASA through Hubble Fellowship grant #HST-HF2-51377 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. Support for PFH was provided by an Alfred P. Sloan Research Fellowship, NASA ATP Grant NNX14AH35G, and NSF Collaborative Research Grant #1411920 and CAREER grant #1455342. CAFG was supported by NSF through grants AST-1412836 and AST-1517491, by NASA through grant NNX15AB22G, and by STScI through grants HST-AR-14293.001-A and HST-GO-14268.022-A. DK acknowledges support from the NSF grant AST-1412153 and Cottrell Scholar Award from the Research Corporation for Science Advancement. EQ was supported by NASA ATP grant 12-ATP12-0183, a Simons Investigator award from the Simons Foundation, and the David and Lucile Packard Foundation.", revision_no = "12", abstract = "We study the spatially resolved (sub-kpc) gas velocity dispersion (σ)--star formation rate (SFR) relation in the FIRE-2 (Feedback in Realistic Environments) cosmological simulations. We specifically focus on Milky Way mass disk galaxies at late times. In agreement with observations, we find a relatively flat relationship, with σ ≈ 15−30 km/s in neutral gas across 3 dex in SFRs. We show that higher dense gas fractions (ratios of dense gas to neutral gas) and SFRs are correlated at constant σ. Similarly, lower gas fractions (ratios of gas to stellar mass) are correlated with higher σ at constant SFR. The limits of the σ-Σ_(SFR) relation correspond to the onset of strong outflows. We see evidence of \"on-off\" cycles of star formation in the simulations, corresponding to feedback injection timescales of 10-100 Myr, where SFRs oscillate about equilibrium SFR predictions. Finally, SFRs and velocity dispersions in the simulations agree well with feedback-regulated and marginally stable gas disk (Toomre's Q=1) model predictions, and the data effectively rule out models assuming that gas turns into stars at (low) constant efficiency (i.e., 1% per free-fall time). And although the simulation data do not entirely exclude gas accretion/gravitationally powered turbulence as a driver of σ, it appears to be strongly subdominant to stellar feedback in the simulated galaxy disks.", } @techreport {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/99015, title ="The Architecture of the LISA Science Analysis", author = "Teukolsky, Saul A. and Vallisneri, Michele", month = "September", year = "2019", doi = "10.26206/NTBV-YA50", url = "https://resolver.caltech.edu/CaltechAUTHORS:20191002-102632020", note = "© September 2019. \n\nThis work had its inception at the Architecture of the LISA Science Analysis study funded by the W. M. Keck Institute for Space Studies. The study organizers and all study participants are deeply grateful to KISS Executive Director Michele Judd and to her amazing staff for creating the perfect environment for insight, creativity, and collegiality. Deirdre Shoemaker acknowledges support from NSF award PHY1806580. Michele Vallisneri, Alvin Chua, Curt Cutler, and Chad Galley acknowledge support from the JPL RTD program. Part of this work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Government sponsorship acknowledged.", revision_no = "18", abstract = "The space-based gravitational-wave (henceforth, GW!) observatory LISA (Amaro-Seoane et al., 2017) will o˙er unparalleled science returns, including a view of massive black hole mergers up to high redshifts, precision tests of general relativity and black hole structure, a census of thousands of compact binaries in the Galaxy, and the possibility of detecting stochastic signals from the early Universe.\nWhile the Mock LISA Data Challenges (2006–2011) gave us confidence that LISA will be able to fulfill its scientific potential, we still have a rather incomplete idea of what the end-to-end LISA science analysis should look like. The task at hand is substantial:\n1) Our data reduction process needs to ensure the phase coherence of GW measurements across data gaps and instrument glitches over multiple years.\n2) Our waveform models need to reach part-in-105 accuracy to maximize the science payo˙ of the mission, with suÿcient computational eÿciency to sample parameter space broadly.\n3) Our algorithms need to resolve thousands of individual sources of di˙erent types and strengths, all of them superimposed on the same multi-year dataset, while simultaneously characterizing the underlying noise-like stochastic background.\n4) Our catalogs need to represent the complex and high-dimensional joint distributions of estimated source parameters for all sources.\nIt is tempting to assume that current algorithms and prototype codes will scale up to this challenge, thanks to the greatly increased computational power that will become available by the time of LISA’s launch in the early 2030s. In reality, harnessing that power will require very di˙erent methods, adapted to future high-performance computational architectures that we can only glimpse now. Thus, we need to begin our exploration at this time, seeking inspiration from other disciplines (e.g., big data processing, computational biology, the most advanced applications in astroinformatics) and learning to pose the same physical questions in di˙erent, future-proof ways—or even daring to imagine questions that will be tractable only with future machines.\nThe broad objective of this study was to imagine how evolved or rethought data analysis algorithms and source-modeling codes will perform the LISA science analysis on the computers of the future, with the hope of guiding LISA science and data analysis research and development in the years to come.", } @misc {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/103722, title ="Studying Black Holes on Horizon Scales with VLBI Ground Arrays", author = "Blackburn, Lindy and Doeleman, Sheperd", journal = "arXiv", month = "September", year = "2019", url = "https://resolver.caltech.edu/CaltechAUTHORS:20200604-151518950", revision_no = "9", abstract = "High-resolution imaging of supermassive black holes is now possible, with new applications to testing general relativity and horizon-scale accretion and relativistic jet formation processes. Over the coming decade, the EHT will propose to add new strategically placed VLBI elements operating at 1.3mm and 0.87mm wavelength. In parallel, development of next-generation backend instrumentation, coupled with high throughput correlation architectures, will boost sensitivity, allowing the new stations to be of modest collecting area while still improving imaging fidelity and angular resolution. The goal of these efforts is to move from imaging static horizon scale structure to dynamic reconstructions that capture the processes of accretion and jet launching in near real time.", } @misc {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/98840, title ="ATLAS Probe: Breakthrough Science of Galaxy Evolution, Cosmology, Milky Way, and the Solar System", author = "Wang, Yun and Dickinson, Mark", journal = "arXiv", month = "August", year = "2019", url = "https://resolver.caltech.edu/CaltechAUTHORS:20190925-085020406", revision_no = "10", abstract = "ATLAS (Astrophysics Telescope for Large Area Spectroscopy) is a concept for a NASA probe-class space mission. It is the spectroscopic follow-up mission to WFIRST, boosting its scientific return by obtaining deep NIR & MIR slit spectroscopy for most of the galaxies imaged by the WFIRST High Latitude Survey at z>0.5. ATLAS will measure accurate and precise redshifts for ~200M galaxies out to z=7 and beyond, and deliver spectra that enable a wide range of diagnostic studies of the physical properties of galaxies over most of cosmic history. ATLAS and WFIRST together will produce a definitive 3D map of the Universe over 2000 sq deg. ATLAS Science Goals are: (1) Discover how galaxies have evolved in the cosmic web of dark matter from cosmic dawn through the peak era of galaxy assembly. (2) Discover the nature of cosmic acceleration. (3) Probe the Milky Way's dust-enshrouded regions, reaching the far side of our Galaxy. (4) Discover the bulk compositional building blocks of planetesimals formed in the outer Solar System. These flow down to the ATLAS Scientific Objectives: (1A) Trace the relation between galaxies and dark matter with less than 10% shot noise on relevant scales at 1