We study AT2024kmq and AT2024lhc, two tidal disruption events (TDEs) with blue featureless spectra associated with high-mass black holes ($M_{\\rm BH}\\sim 10^8\\, \\mathrm{ M}_\\odot$). Both events show optical precursors consistent with shock dissipation from stream self-intersection. Their X-ray emission is luminous ($L_{\\rm X}\\sim 10^{44}\\, {\\rm erg\\, s^{-1}}$), highly variable (with minimum observed variability time-scales of 1.3 and 4.8 h for factor of ∼3 flux changes), long-lasting (>1 yr), emerging no later than the optical peak, and well characterized by power laws with $1.7\\lt \\Gamma \\lt 3$ (where $f_\\nu \\propto \\nu ^{1-\\Gamma }$). The X-ray properties and radio non-detections support a compact corona ($\\lesssim 10 r_{\\rm g}$) producing Comptonized X-ray emission. Using all published featureless TDEs, we find statistically significant bimodality in the distribution of their peak ultraviolet/optical blackbody luminosities and radii. We assemble a comparison TDE sample with early-time X-ray observations with eROSITA, in which we find different $M_{\\rm BH}$ distributions in TDEs with different X-ray spectral evolution properties: low-mass black holes ($M_{\\rm BH} \\sim 10^6 \\mathrm{ M}_\\odot$) remain soft ($\\Gamma \\gt 4$) within $t\\lesssim 2$ yr, intermediate masses ($\\sim 10^7 \\mathrm{ M}_\\odot$) transition from soft to hard at $\\sim$1 yr, while high masses ($\\sim 10^8 \\mathrm{ M}_\\odot$) are hard ($1.5\\lt \\Gamma \\lesssim 3$) from the outset. We interpret this result as evidence that the soft-to-hard state transition in TDEs occurs at the critical threshold of $\\dot{M}_{\\rm acc} \\sim 0.03 \\dot{M}_{\\rm Edd}$ (similar to X-ray binaries), using the fact that the transition time-scale predicted by simple disc theory scales with black hole mass as $t_{\\rm tr}\\propto M_{\\rm BH}^{-3/4}$.
", "doi": "10.1093/mnras/stag920", "issn": "0035-8711", "publisher": "Royal Astronomical Society", "publication": "Monthly Notices of the Royal Astronomical Society", "publication_date": "2026-06", "series_number": "2", "volume": "549", "issue": "2", "pages": "stag920" }, { "id": "authors:r494d-8jk37", "collection": "authors", "collection_id": "r494d-8jk37", "cite_using_url": "https://authors.library.caltech.edu/records/r494d-8jk37", "type": "article", "title": "Prediscovery Activity of New Interstellar Object 3I/ATLAS: Rapid Brightening from 6 to 4 au", "author": [ { "family_name": "Ye \u53f6", "given_name": "Quanzhi \u6cc9\u5fd7", "orcid": "0000-0002-4838-7676" }, { "family_name": "Kelley", "given_name": "Michael S. P.", "orcid": "0000-0002-6702-7676" }, { "family_name": "Hsieh", "given_name": "Henry H.", "orcid": "0000-0001-7225-9271" }, { "family_name": "Bellm", "given_name": "Eric C.", "orcid": "0000-0001-8018-5348" }, { "family_name": "Chen", "given_name": "Tracy X.", "orcid": "0000-0001-9152-6224", "clpid": "Chen-Tracy-X" }, { "family_name": "Dekany", "given_name": "Richard", "orcid": "0000-0002-5884-7867", "clpid": "Dekany-Richard" }, { "family_name": "Drake", "given_name": "Andrew", "orcid": "0000-0003-0228-6594", "clpid": "Drake-Andrew" }, { "family_name": "Groom", "given_name": "Steven L.", "orcid": "0000-0001-5668-3507", "clpid": "Groom-Steven-L" }, { "family_name": "Helou", "given_name": "George", "orcid": "0000-0003-3367-3415", "clpid": "Helou-G" }, { "family_name": "Kulkarni", "given_name": "Shrinivas R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" }, { "family_name": "Prince", "given_name": "Thomas A.", "orcid": "0000-0002-8850-3627", "clpid": "Prince-T-A" }, { "family_name": "Riddle", "given_name": "Reed", "orcid": "0000-0002-0387-370X", "clpid": "Riddle-Reed" } ], "abstract": "We report on the prediscovery observations and constraints of the new interstellar comet 3I/2025 N1 (ATLAS), made by the Zwicky Transient Facility, for the inbound leg of the comet out to a heliocentric distance of rh = 17 au, or approximately a year before its discovery. We find that 3I/ATLAS has been active inward of a heliocentric distance of at least rh = 6.5 au. The comet followed a brightening rate of ∝ r_h^(−3.8), which is significantly steeper than that of the only other known interstellar comet, 2I/Borisov, and is more consistent with dynamically old long-period comets and short-period comets in the solar system. By measuring the brightening of the dust coma, we estimate that 3I had a dust production rate of M_d \u0307 ∼ 5 kg s\u207b¹ in 2025 early May (rh ∼ 6 au), increasing to M_d \u0307 ∼ 5 kg s\u207b¹ toward 2025 mid-July (rh ∼ 4 au) assuming 100 μm dust grains, in line with the more recent Hubble Space Telescope measurement made at rh = 3.8 au. Comparison with the prediscovery photometry by the Transiting Exoplanet Survey Satellite suggested that 3I started producing constant dust outflow probably around rh ∼ 9 au, coinciding with the turn-on distance of CO2 ice. We also conduct a deep search of 3I/ATLAS with multiple nights of data taken in 2024, when the comet was at rh = 13–17 au, and conclude that the comet was no brighter than 2–5 mag above the coma or bare-nucleus lightcurves. This suggests that the comet did not exhibit strong outbursts during these periods, consistent with 2I/Borisov as well as most long-period solar system comets.
", "doi": "10.3847/2041-8213/ae147b", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "2025-11-01", "series_number": "1", "volume": "993", "issue": "1", "pages": "L31" }, { "id": "authors:985q2-ndq40", "collection": "authors", "collection_id": "985q2-ndq40", "cite_using_url": "https://authors.library.caltech.edu/records/985q2-ndq40", "type": "article", "title": "QZO: A Catalog of 5 Million Quasars from the Zwicky Transient Facility", "author": [ { "family_name": "Nakoneczny", "given_name": "S. J.", "orcid": "0000-0003-2130-7143", "clpid": "Nakoneczny-Szymon-J" }, { "family_name": "Graham", "given_name": "M. J.", "orcid": "0000-0002-3168-0139", "clpid": "Graham-M-J" }, { "family_name": "Stern", "given_name": "D.", "orcid": "0000-0003-2686-9241", "clpid": "Stern-D" }, { "family_name": "Helou", "given_name": "G.", "orcid": "0000-0003-3367-3415", "clpid": "Helou-G" }, { "family_name": "Djorgovski", "given_name": "S. G.", "orcid": "0000-0002-0603-3087", "clpid": "Djorgovski-S-G" }, { "family_name": "Bellm", "given_name": "E. C.", "orcid": "0000-0001-8018-5348" }, { "family_name": "Chen", "given_name": "T. X.", "orcid": "0000-0001-9152-6224", "clpid": "Chen-Tracy-X" }, { "family_name": "Dekany", "given_name": "R.", "orcid": "0000-0002-5884-7867", "clpid": "Dekany-Richard" }, { "family_name": "Drake", "given_name": "A.", "orcid": "0000-0003-0228-6594", "clpid": "Drake-Andrew" }, { "family_name": "Mahabal", "given_name": "A. A.", "orcid": "0000-0003-2242-0244", "clpid": "Mahabal-A-A" }, { "family_name": "Prince", "given_name": "T. A.", "orcid": "0000-0002-8850-3627", "clpid": "Prince-T-A" }, { "family_name": "Riddle", "given_name": "R.", "orcid": "0000-0002-0387-370X", "clpid": "Riddle-Reed" }, { "family_name": "Rusholme", "given_name": "B.", "orcid": "0000-0001-7648-4142", "clpid": "Rusholme-Benjamin" }, { "family_name": "Sravan", "given_name": "N." } ], "abstract": "Machine learning methods are well established in the classification of quasars (QSOs). However, the advent of light-curve observations adds a great amount of complexity to the problem. Our goal is to use the Zwicky Transient Facility (ZTF) to create a catalog of QSOs. We process the ZTF DR20 light curves with a transformer artificial neural network and combine different surveys with extreme gradient boosting. Based on ZTF g-band and Wide-field Infrared Survey Explorer (WISE) observations, we find 4,849,574 objects classified as QSOs with confidence higher than 90% (QZO). We robustly classify objects fainter than the 5σ signal-to-noise ratio (SNR) limit at g = 20.8 by requiring g < nobs/80 + 20.375. For 33% of QZO objects, with available WISE data, we publish redshifts with estimated error Δz/(1 + z) = 0.14. We find that ZTF classification is superior to the Pan-STARRS static bands, and on par with WISE and Gaia measurements, but the light curves provide the most important features for QSO classification in the ZTF data set. Using ZTF g-band data with at least 100 observational epochs per light curve, we obtain a 97% F1 score for QSOs. We find that with 3 day median cadence, a survey time span of at least 900 days is required to achieve a 90% QSO F1 score. However, one can obtain the same score with a survey time span of 1800 days and the median cadence prolonged to 12 days.
", "doi": "10.3847/1538-4357/adf4e4", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2025-10-10", "series_number": "1", "volume": "992", "issue": "1", "pages": "153" }, { "id": "authors:2r52b-hkq34", "collection": "authors", "collection_id": "2r52b-hkq34", "cite_using_url": "https://authors.library.caltech.edu/records/2r52b-hkq34", "type": "article", "title": "Multiwavelength analysis of AT 2023sva: a luminous orphan afterglow with evidence for a structured jet", "author": [ { "family_name": "Srinivasaragavan", "given_name": "Gokul P.", "orcid": "0000-0002-6428-2700" }, { "family_name": "Perley", "given_name": "Daniel A.", "orcid": "0000-0001-8472-1996" }, { "family_name": "Ho", "given_name": "Anna Y. Q.", "orcid": "0000-0002-9017-3567" }, { "family_name": "O'Connor", "given_name": "Brendan", "orcid": "0000-0002-9700-0036" }, { "family_name": "Postigo", "given_name": "Antonio de Ugarte", "orcid": "0000-0001-7717-5085" }, { "family_name": "Sarin", "given_name": "Nikhil", "orcid": "0000-0003-2700-1030" }, { "family_name": "Cenko", "given_name": "S. Bradley", "orcid": "0000-0003-1673-970X" }, { "family_name": "Sollerman", "given_name": "Jesper", "orcid": "0000-0003-1546-6615" }, { "family_name": "Rhodes", "given_name": "Lauren", "orcid": "0000-0003-2705-4941" }, { "family_name": "Green", "given_name": "David A.", "orcid": "0000-0003-3189-9998" }, { "family_name": "Svinkin", "given_name": "Dmitry S.", "orcid": "0000-0002-2208-2196" }, { "family_name": "Bhalerao", "given_name": "Varun", "orcid": "0000-0002-6112-7609" }, { "family_name": "Waratkar", "given_name": "Gaurav", "orcid": "0000-0003-3630-9440" }, { "family_name": "Nayana", "given_name": "A. J." }, { "family_name": "Chandra", "given_name": "Poonam", "orcid": "0000-0002-0844-6563" }, { "family_name": "Miller", "given_name": "M. Coleman" }, { "family_name": "Malesani", "given_name": "Daniele B.", "orcid": "0000-0002-7517-326X" }, { "family_name": "Ryan", "given_name": "Geoffrey", "orcid": "0000-0001-9068-7157" }, { "family_name": "Srijan", "given_name": "Suryansh" }, { "family_name": "Bellm", "given_name": "Eric C.", "orcid": "0000-0001-8018-5348" }, { "family_name": "Burns", "given_name": "Eric" }, { "family_name": "Titterington", "given_name": "David J." }, { "family_name": "Stone", "given_name": "Maria B.", "orcid": "0000-0002-2931-0593" }, { "family_name": "Purdum", "given_name": "Josiah", "orcid": "0000-0003-1227-3738", "clpid": "Purdum-Josiah" }, { "family_name": "Ahumada", "given_name": "Tom\u00e1s", "orcid": "0000-0002-2184-6430", "clpid": "Ahumada-Tom\u00e1s" }, { "family_name": "Anupama", "given_name": "G. C.", "orcid": "0000-0003-3533-7183" }, { "family_name": "Barway", "given_name": "Sudhanshu", "orcid": "0000-0002-3927-5402" }, { "family_name": "Coughlin", "given_name": "Michael W.", "orcid": "0000-0002-8262-2924" }, { "family_name": "Drake", "given_name": "Andrew", "orcid": "0000-0003-0228-6594", "clpid": "Drake-Andrew" }, { "family_name": "Fender", "given_name": "Rob" }, { "family_name": "Fern\u00e1ndez", "given_name": "Jos\u00e9 F. Ag\u00fc\u00ed", "orcid": "0000-0001-6991-7616" }, { "family_name": "Frederiks", "given_name": "Dmitry D.", "orcid": "0000-0002-1153-6340" }, { "family_name": "Geier", "given_name": "Stefan", "orcid": "0000-0001-9456-8358" }, { "family_name": "Graham", "given_name": "Matthew J.", "orcid": "0000-0002-3168-0139", "clpid": "Graham-M-J" }, { "family_name": "Kasliwal", "given_name": "Mansi M.", "orcid": "0000-0002-5619-4938", "clpid": "Kasliwal-M-M" }, { "family_name": "Kulkarni", "given_name": "S. R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" }, { "family_name": "Kumar", "given_name": "Harsh", "orcid": "0000-0003-0871-4641" }, { "family_name": "Li", "given_name": "Maggie L.", "orcid": "0009-0001-6911-9144", "clpid": "Li-Maggie-L" }, { "family_name": "Laher", "given_name": "Russ R.", "orcid": "0000-0003-2451-5482", "clpid": "Laher-R-R" }, { "family_name": "Lysenko", "given_name": "Alexandra L." }, { "family_name": "Parwani", "given_name": "Gopal", "orcid": "0009-0006-8646-5002" }, { "family_name": "Perley", "given_name": "Richard A.", "orcid": "0000-0001-7097-8360" }, { "family_name": "Ridnaia", "given_name": "Anna V.", "orcid": "0000-0001-9477-5437" }, { "family_name": "Salgundi", "given_name": "Anirudh", "orcid": "0000-0003-3173-4691" }, { "family_name": "Smith", "given_name": "Roger", "orcid": "0000-0001-7062-9726", "clpid": "Smith-R-M" }, { "family_name": "Sravan", "given_name": "Niharika" }, { "family_name": "Swain", "given_name": "Vishwajeet", "orcid": "0000-0002-7942-8477" }, { "family_name": "Th\u00f6ne", "given_name": "Christina C.", "orcid": "0000-0002-7978-7648" }, { "family_name": "Tsvetkova", "given_name": "Anastasia E.", "orcid": "0000-0003-0292-6221" }, { "family_name": "Ulanov", "given_name": "Mikhail V.", "orcid": "0000-0002-0076-5228" }, { "family_name": "Vail", "given_name": "Jada" }, { "family_name": "Wise", "given_name": "Jacob L.", "orcid": "0000-0003-0733-2916" }, { "family_name": "Wold", "given_name": "Avery", "orcid": "0000-0002-9998-6732", "clpid": "Wold-Avery" } ], "abstract": "We present multiwavelength analysis of ZTF23abelseb (AT 2023sva), an optically discovered fast-fading (\u2060Δm_r = 2.2 mag in Δt = 0.74d), luminous (M_r ~ -30.0\u2060 mag), and red (\u2060g - r = 0.50 mag) transient at z = 2.28 with accompanying luminous radio emission. AT 2023sva does not possess a γ-ray burst (GRB) counterpart to an isotropic equivalent energy limit of Eγ,iso < 1.6 x 10\u2075² erg, determined through searching γ-ray satellite archives between the last non-detection and first detection, making it the sixth example of an optically discovered afterglow with a redshift measurement and no detected GRB counterpart. We analyse AT 2023sva’s optical, radio, and X-ray observations to characterize the source. From radio analyses, we find the clear presence of strong interstellar scintillation (ISS) 72 d after the initial explosion, allowing us to place constraints on the source’s angular size and bulk Lorentz factor. When comparing the source sizes derived from ISS of orphan events to those of the classical GRB population, we find orphan events have statistically smaller source sizes. We also utilize Bayesian techniques to model the multiwavelength afterglow. Within this framework, we find evidence that AT 2023sva possesses a shallow power-law structured jet viewed slightly off-axis (\u2060\u2060θ_v = 0.07 ± 0.02) just outside of the jet’s core opening angle (\u2060\u2060θ_c = 0.06 ± 0.02). We determine this is likely the reason for the lack of a detected GRB counterpart, but also investigate other scenarios. AT 2023sva’s evidence for possessing a structured jet stresses the importance of broadening orphan afterglow search strategies to a diverse range of GRB jet angular energy profiles, to maximize the return of future optical surveys.
", "doi": "10.1093/mnras/staf290", "issn": "0035-8711", "publisher": "Royal Astronomical Society", "publication": "Monthly Notices of the Royal Astronomical Society", "publication_date": "2025-03", "series_number": "1", "volume": "538", "issue": "1", "pages": "351-372" }, { "id": "authors:bwecf-fzy49", "collection": "authors", "collection_id": "bwecf-fzy49", "cite_using_url": "https://authors.library.caltech.edu/records/bwecf-fzy49", "type": "article", "title": "ZTF SN Ia DR2: The spectral diversity of Type Ia supernovae in a volume-limited sample", "author": [ { "family_name": "Burgaz", "given_name": "U.", "orcid": "0000-0003-0126-3999" }, { "family_name": "Maguire", "given_name": "K.", "orcid": "0000-0002-9770-3508" }, { "family_name": "Dimitriadis", "given_name": "G.", "orcid": "0000-0001-9494-179X" }, { "family_name": "Harvey", "given_name": "L.", "orcid": "0000-0003-3393-9383" }, { "family_name": "Senzel", "given_name": "R.", "orcid": "0009-0002-0243-8199" }, { "family_name": "Sollerman", "given_name": "J.", "orcid": "0000-0003-1546-6615" }, { "family_name": "Nordin", "given_name": "J.", "orcid": "0000-0001-8342-6274" }, { "family_name": "Galbany", "given_name": "L.", "orcid": "0000-0002-1296-6887" }, { "family_name": "Rigault", "given_name": "M.", "orcid": "0000-0002-8121-2560" }, { "family_name": "Smith", "given_name": "M.", "orcid": "0000-0002-3321-1432" }, { "family_name": "Goobar", "given_name": "A.", "orcid": "0000-0002-4163-4996" }, { "family_name": "Johansson", "given_name": "J.", "orcid": "0000-0001-5975-290X" }, { "family_name": "Rosnet", "given_name": "P.", "orcid": "0000-0002-6099-7565" }, { "family_name": "Alburai", "given_name": "A.", "orcid": "0009-0007-2731-5562" }, { "family_name": "Amenouche", "given_name": "M.", "orcid": "0009-0006-7454-3579" }, { "family_name": "Deckers", "given_name": "M.", "orcid": "0000-0001-8857-9843" }, { "family_name": "Dhawan", "given_name": "S.", "orcid": "0000-0002-2376-6979" }, { "family_name": "Ginolin", "given_name": "M.", "orcid": "0009-0004-5311-9301" }, { "family_name": "Kim", "given_name": "Y.-L.", "orcid": "0000-0002-1031-0796" }, { "family_name": "Miller", "given_name": "A. A.", "orcid": "0000-0001-9515-478X" }, { "family_name": "Muller-Bravo", "given_name": "T. E.", "orcid": "0000-0003-3939-7167" }, { "family_name": "Nugent", "given_name": "P. E.", "orcid": "0000-0002-3389-0586" }, { "family_name": "Terwel", "given_name": "J. H.", "orcid": "0000-0001-9834-3439" }, { "family_name": "Dekany", "given_name": "R.", "orcid": "0000-0002-5884-7867", "clpid": "Dekany-Richard" }, { "family_name": "Drake", "given_name": "A.", "clpid": "Drake-Andrew" }, { "family_name": "Graham", "given_name": "M. J.", "orcid": "0000-0002-3168-0139", "clpid": "Graham-M-J" }, { "family_name": "Groom", "given_name": "S. L.", "orcid": "0000-0001-5668-3507" }, { "family_name": "Kasliwal", "given_name": "M. M.", "orcid": "0000-0002-5619-4938", "clpid": "Kasliwal-M-M" }, { "family_name": "Kulkarni", "given_name": "S. R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" }, { "family_name": "Nolan", "given_name": "K.", "orcid": "0009-0002-4724-7118", "clpid": "Nolan-Kira" }, { "family_name": "Nir", "given_name": "G.", "orcid": "0000-0002-7501-5579" }, { "family_name": "Riddle", "given_name": "R. L.", "orcid": "0000-0002-0387-370X", "clpid": "Riddle-Reed-L" }, { "family_name": "Rusholme", "given_name": "B.", "orcid": "0000-0001-7648-4142", "clpid": "Rusholme-Benjamin" }, { "family_name": "Sharma", "given_name": "Y.", "orcid": "0000-0003-4531-1745", "clpid": "Sharma-Yashvi" } ], "abstract": "More than 3000 spectroscopically confirmed Type Ia supernovae (SNe Ia) are presented in the second data release (DR2) of the Zwicky Transient Facility survey. In this paper we detail the spectral properties of 482 SNe Ia near maximum light, up to a redshift limit of z\u2004≤\u20040.06. We measured the velocities and pseudo-equivalent widths (pEW) of key spectral features (Si\u202fIIλ5972 and Si\u202fIIλ6355) and investigated the relation between the properties of the spectral features and the photometric properties from the SALT2 light-curve parameters as a function of spectroscopic sub-class. We discuss the non-negligible impact of host galaxy contamination on SN Ia spectral classifications, and we investigate the accuracy of spectral template matching of the DR2 sample. We define a new subclass of underluminous SNe Ia (04gs-like) that lie spectroscopically between normal SNe Ia and transitional 86G-like SNe Ia (stronger Si\u202fIIλ5972 than normal SNe Ia, but significantly weaker Ti\u202fII features than 86G-like SNe). We model these 04gs-like SN Ia spectra using the radiative-transfer spectral synthesis code TARDIS and show that cooler temperatures alone are unable to explain their spectra; some changes in elemental abundances are also required. However, the broad continuity in spectral properties seen from bright (91T-like) to faint normal SN Ia, including the transitional and 91bg-like SNe Ia, suggests that variations within a single explosion model may be able to explain their behaviour.
", "doi": "10.1051/0004-6361/202450386", "issn": "0004-6361", "publisher": "EDP Sciences", "publication": "Astronomy and Astrophysics", "publication_date": "2025-02", "volume": "694", "pages": "A9" }, { "id": "authors:n23nm-f6g05", "collection": "authors", "collection_id": "n23nm-f6g05", "cite_using_url": "https://authors.library.caltech.edu/records/n23nm-f6g05", "type": "article", "title": "Photometric prioritization of neutron star merger candidates", "author": [ { "family_name": "Ofek", "given_name": "Eran O", "orcid": "0000-0002-6786-8774" }, { "family_name": "Strotjohann", "given_name": "Nora L", "orcid": "0000-0002-4667-6730" }, { "family_name": "Arcavi", "given_name": "Iair", "orcid": "0000-0001-7090-4898" }, { "family_name": "Gal-Yam", "given_name": "Avishay", "orcid": "0000-0002-3653-5598" }, { "family_name": "Kushnir", "given_name": "Doron" }, { "family_name": "Waxman", "given_name": "Eli", "orcid": "0000-0002-9038-5877" }, { "family_name": "Kasliwal", "given_name": "Mansi M", "orcid": "0000-0002-5619-4938", "clpid": "Kasliwal-M-M" }, { "family_name": "Drake", "given_name": "Andrew", "orcid": "0000-0003-0228-6594", "clpid": "Drake-Andrew" }, { "family_name": "Graham", "given_name": "Matthew", "orcid": "0000-0002-3168-0139", "clpid": "Graham-M-J" }, { "family_name": "Purdum", "given_name": "Josiah", "orcid": "0000-0003-1227-3738", "clpid": "Purdum-Josiah-N" }, { "family_name": "Rusholme", "given_name": "Ben", "orcid": "0000-0001-7648-4142", "clpid": "Rusholme-Benjamin" }, { "family_name": "Sharma", "given_name": "Yashvi", "orcid": "0000-0003-4531-1745", "clpid": "Sharma-Yashvi" }, { "family_name": "Smith", "given_name": "Roger", "orcid": "0000-0001-7062-9726", "clpid": "Smith-R-M" }, { "family_name": "Wold", "given_name": "Avery", "orcid": "0000-0002-9998-6732", "clpid": "Wold-Avery" }, { "family_name": "Healy", "given_name": "Brian F", "orcid": "0000-0002-7718-7884" } ], "abstract": "Rapid identification of the optical counterparts of neutron star (NS) merger events discovered by gravitational wave detectors may require observing a large error region and sifting through a large number of transients to identify the object of interest. Given the expense of spectroscopic observations, a question arises: How can we utilize photometric observations for candidate prioritization, and what kinds of photometric observations are needed to achieve this goal? NS merger kilonova exhibits low ejecta mass (∼5 × 10\u207b² M\u2299) and a rapidly evolving photospheric radius (with a velocity ∼0.2c). As a consequence, these sources display rapid optical-flux evolution. Indeed, selection based on fast flux variations is commonly used for young supernovae and NS mergers. In this study, we leverage the best currently available flux-limited transient survey – the Zwicky Transient Facility Bright Transient Survey – to extend and quantify this approach. We focus on selecting transients detected in a 3-day cadence survey and observed at a one-day cadence. We explore their distribution in the phase space defined by g–r, $\\dot{g}$, and $\\dot{r}$. Our analysis demonstrates that for a significant portion of the time during the first week, the kilonova AT 2017gfo stands out in this phase space. It is important to note that this investigation is subject to various biases and challenges; nevertheless, it suggests that certain photometric observations can be leveraged to identify transients with the highest probability of being fast-evolving events. We also find that a large fraction (≈75 per cent) of the transient candidates with $\\vert\\dot{g}\\vert>0.7$ mag d−1, are cataclysmic variables or active galactic nuclei with radio counterparts.
", "doi": "10.1093/mnras/stad3380", "issn": "0035-8711", "publisher": "Royal Astronomical Society", "publication": "Monthly Notices of the Royal Astronomical Society", "publication_date": "2024-01", "series_number": "2", "volume": "527", "issue": "2", "pages": "3741-3748" }, { "id": "authors:9byqp-c5d28", "collection": "authors", "collection_id": "9byqp-c5d28", "cite_using_url": "https://authors.library.caltech.edu/records/9byqp-c5d28", "type": "article", "title": "SRGeJ045359.9+622444: A 55 Minute Period Eclipsing AM Canum Venaticorum Star Discovered from a Joint SRG/eROSITA + ZTF Search", "author": [ { "family_name": "Rodriguez", "given_name": "Antonio C.", "orcid": "0000-0003-4189-9668", "clpid": "Rodriguez-Antonio-C" }, { "family_name": "Galiullin", "given_name": "Ilkham", "orcid": "0000-0001-5778-2355" }, { "family_name": "Gilfanov", "given_name": "Marat", "orcid": "0000-0003-4029-6769" }, { "family_name": "Kulkarni", "given_name": "Shrinivas R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" }, { "family_name": "Khamitov", "given_name": "Irek" }, { "family_name": "Bikmaev", "given_name": "Ilfan" }, { "family_name": "van Roestel", "given_name": "Jan", "orcid": "0000-0002-2626-2872" }, { "family_name": "Yungelson", "given_name": "Lev", "orcid": "0000-0003-2252-430X" }, { "family_name": "El-Badry", "given_name": "Kareem", "orcid": "0000-0002-6871-1752", "clpid": "El-Badry-Kareem" }, { "family_name": "Sunayev", "given_name": "Rashid" }, { "family_name": "Prince", "given_name": "Thomas A.", "orcid": "0000-0002-8850-3627", "clpid": "Prince-T-A" }, { "family_name": "Buntov", "given_name": "Mikhail" }, { "family_name": "Caiazzo", "given_name": "Ilaria", "orcid": "0000-0002-4770-5388", "clpid": "Caiazzo-Ilaria" }, { "family_name": "Drake", "given_name": "Andrew", "orcid": "0000-0003-0228-6594", "clpid": "Drake-Andrew" }, { "family_name": "Gorbachev", "given_name": "Mark" }, { "family_name": "Graham", "given_name": "Matthew J.", "orcid": "0000-0002-3168-0139", "clpid": "Graham-M-J" }, { "family_name": "Gumerov", "given_name": "Rustam" }, { "family_name": "Irtuganov", "given_name": "Eldar" }, { "family_name": "Laher", "given_name": "Russ R.", "orcid": "0000-0003-2451-5482", "clpid": "Laher-R-R" }, { "family_name": "Masci", "given_name": "Frank J.", "orcid": "0000-0002-8532-9395", "clpid": "Masci-Frank-J" }, { "family_name": "Medvedev", "given_name": "Pavel", "orcid": "0000-0002-9380-8708" }, { "family_name": "Purdum", "given_name": "Josiah", "orcid": "0000-0003-1227-3738", "clpid": "Purdum-Josiah" }, { "family_name": "Sakhibullin", "given_name": "Nail" }, { "family_name": "Sklyanov", "given_name": "Alexander" }, { "family_name": "Smith", "given_name": "Roger", "orcid": "0000-0001-7062-9726", "clpid": "Smith-R-M" }, { "family_name": "Szkody", "given_name": "Paula", "orcid": "0000-0003-4373-7777" }, { "family_name": "Vanderbosch", "given_name": "Zachary P.", "orcid": "0000-0002-0853-3464", "clpid": "Vanderbosch-Zachary-P" } ], "abstract": "AM Canum Venaticorum (AM CVn) systems are ultracompact binaries where a white dwarf accretes from a helium-rich degenerate or semidegenerate donor. Some AM CVn systems will be among the loudest sources of gravitational waves for the upcoming Laser Interferometer Space Antenna; yet the formation channel of AM CVns remains uncertain. We report the study and characterization of a new eclipsing AM CVn, SRGeJ045359.9+622444 (hereafter, SRGeJ0453), discovered from a joint Spektrum-Roentgen-Gamma (SRG) Extended Roentgen Survey with an Imaging Telescope Array (eROSITA) mission and Zwicky Transient Facility program to identify cataclysmic variables (CVs). We obtained optical photometry to confirm the eclipse of SRGeJ0453 and determine the orbital period to be P_(orb) = 55.0802 ± 0.0003 min. We constrain the binary parameters by modeling the high-speed photometry and radial-velocity curves and find Mdonor = 0.044 ± 0.024M\u2299 and Rdonor = 0.078 ± 0.012R\u2299. The X-ray spectrum is approximated by a power-law model with an unusually flat photon index of Γ ∼ 1 previously seen in magnetic CVs with SRG/eROSITA, but verifying that the magnetic nature of SRGeJ0453 requires further investigation. Optical spectroscopy suggests that the donor star of SRGeJ0453 could have initially been a He star or a He white dwarf. SRGeJ0453 is the ninth eclipsing AM CVn system published to date, and its lack of optical outbursts have made it elusive in previous surveys. The discovery of SRGeJ0453 using joint X-ray and optical surveys highlights the potential for discovering similar systems in the near future.
", "doi": "10.3847/1538-4357/ace698", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2023-09-01", "series_number": "1", "volume": "954", "issue": "1", "pages": "63" }, { "id": "authors:fc0vb-79e92", "collection": "authors", "collection_id": "fc0vb-79e92", "cite_using_url": "https://authors.library.caltech.edu/records/fc0vb-79e92", "type": "article", "title": "Variability-selected Intermediate-mass Black Hole Candidates in Dwarf Galaxies from ZTF and WISE", "author": [ { "family_name": "Ward", "given_name": "Charlotte", "orcid": "0000-0002-4557-6682" }, { "family_name": "Gezari", "given_name": "Suvi", "orcid": "0000-0003-3703-5154" }, { "family_name": "Nugent", "given_name": "Peter", "orcid": "0000-0002-3389-0586" }, { "family_name": "Bellm", "given_name": "Eric C.", "orcid": "0000-0001-8018-5348" }, { "family_name": "Dekany", "given_name": "Richard", "orcid": "0000-0002-5884-7867", "clpid": "Dekany-Richard" }, { "family_name": "Drake", "given_name": "Andrew", "clpid": "Drake-Andrew" }, { "family_name": "Duev", "given_name": "Dmitry A.", "orcid": "0000-0001-5060-8733", "clpid": "Duev-Dmitry-A" }, { "family_name": "Graham", "given_name": "Matthew J.", "orcid": "0000-0002-3168-0139", "clpid": "Graham-M-J" }, { "family_name": "Kasliwal", "given_name": "Mansi M.", "orcid": "0000-0002-5619-4938", "clpid": "Kasliwal-M-M" }, { "family_name": "Kool", "given_name": "Erik C.", "orcid": "0000-0002-7252-3877" }, { "family_name": "Masci", "given_name": "Frank J.", "orcid": "0000-0002-8532-9395", "clpid": "Masci-Frank-J" }, { "family_name": "Riddle", "given_name": "Reed L.", "orcid": "0000-0002-0387-370X", "clpid": "Riddle-Reed-L" } ], "abstract": "While it is difficult to observe the first black hole seeds in the early universe, we can study intermediate-mass black holes (IMBHs) in local dwarf galaxies for clues about their origins. In this paper we present a sample of variability-selected active galactic nuclei (AGN) in dwarf galaxies using optical photometry from the Zwicky Transient Facility (ZTF) and forward-modeled mid-IR photometry of time-resolved Wide-field Infrared Survey Explorer (WISE) co-added images. We found that 44 out of 25,714 dwarf galaxies had optically variable AGN candidates and 148 out of 79,879 dwarf galaxies had mid-IR variable AGN candidates, corresponding to active fractions of 0.17% ± 0.03% and 0.19% ± 0.02%, respectively. We found that spectroscopic approaches to AGN identification would have missed 81% of our ZTF IMBH candidates and 69% of our WISE IMBH candidates. Only nine candidates have been detected previously in radio, X-ray, and variability searches for dwarf galaxy AGN. The ZTF and WISE dwarf galaxy AGN with broad Balmer lines have virial masses of 10\u2075 M\u2299 < M_(BH) < 10\u2077 M\u2299, but for the rest of the sample, BH masses predicted from host galaxy mass range between 10^(5.2) M\u2299 < M_(BH) < 10^(7.25) M\u2299. We found that only 5 of 152 previously reported variability-selected AGN candidates from the Palomar Transient Factory in common with our parent sample were variable in ZTF. We also determined a nuclear supernova fraction of 0.05% ± 0.01% yr\u207b¹ for dwarf galaxies in ZTF. Our ZTF and WISE IMBH candidates show the promise of variability searches for the discovery of otherwise hidden low-mass AGN.
", "doi": "10.3847/1538-4357/ac8666", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2022-09-10", "series_number": "2", "volume": "936", "issue": "2", "pages": "104" } ]