Submitted - 1905.11439.pdf
", "abstract": "The cosmic X-ray background (CXB), which peaks at an energy of \u224830 keV, is produced primarily by emission from accreting supermassive black holes (SMBHs). The CXB therefore serves as a constraint on the integrated SMBH growth in the Universe and the accretion physics and obscuration in active galactic nuclei (AGNs). This paper gives an overview of recent progress in understanding the high-energy (>~10 keV) X-ray emission from AGNs and the synthesis of the CXB, with an emphasis on results from NASA's NuSTAR hard X-ray mission. We then discuss remaining challenges and open questions regarding the nature of AGN obscuration and AGN physics. Finally, we highlight the exciting opportunities for a next-generation, high-resolution hard X-ray mission to achieve the long-standing goal of resolving and characterizing the vast majority of the accreting SMBHs that produce the CXB.", "date": "2019-05-27", "date_type": "published", "publisher": "arXiv", "id_number": "CaltechAUTHORS:20190619-095513937", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190619-095513937", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "Space-Radiation-Laboratory" } ] }, "doi": "10.48550/arXiv.1905.11439", "primary_object": { "basename": "1905.11439.pdf", "url": "https://authors.library.caltech.edu/records/5exb9-thj37/files/1905.11439.pdf" }, "pub_year": "2019", "author_list": "Hickox, R. C.; Civano, F.; et al." }, { "id": "https://authors.library.caltech.edu/records/079rp-w0723", "eprint_id": 96495, "eprint_status": "archive", "datestamp": "2023-08-19 15:01:45", "lastmod": "2025-02-02 20:57:52", "type": "publication_whitepaper", "metadata_visibility": "show", "creators": { "items": [ { "id": "Vulic-N", "name": { "family": "Vulic", "given": "N." }, "orcid": "0000-0001-7855-8336" }, { "id": "Hornschemeier-A-E", "name": { "family": "Hornschemeier", "given": "A. E." }, "orcid": "0000-0001-8667-2681" }, { "id": "Antoniou-V", "name": { "family": "Antoniou", "given": "V." }, "orcid": "0000-0001-7539-1593" }, { "id": "Basu-Zych-A-R", "name": { "family": "Basu-Zych", "given": "A. R." } }, { "id": "Binder-B", "name": { "family": "Binder", "given": "B." } }, { "id": "Fornasini-F-M", "name": { "family": "Fornasini", "given": "F. M." } }, { "id": "F\u00fcrst-F", "name": { "family": "F\u00fcrst", "given": "F." }, "orcid": "0000-0003-0388-0560" }, { "id": "Haberl-F", "name": { "family": "Haberl", "given": "F." } }, { "id": "Heida-M", "name": { "family": "Heida", "given": "M." }, "orcid": "0000-0002-1082-7496" }, { "id": "Lehmer-B-D", "name": { "family": "Lehmer", "given": "B. D." }, "orcid": "0000-0003-2192-3296" }, { "id": "Maccarone-T-J", "name": { "family": "Maccarone", "given": "T. J." }, "orcid": "0000-0003-0976-4755" }, { "id": "Ptak-A", "name": { "family": "Ptak", "given": "A. F." }, "orcid": "0000-0001-5655-1440" }, { "id": "Sivakoff-G-R", "name": { "family": "Sivakoff", "given": "G. R." }, "orcid": "0000-0001-6682-916X" }, { "id": "Tzanavaris-P", "name": { "family": "Tzanavaris", "given": "P." }, "orcid": "0000-0001-5737-5055" }, { "id": "Wik-D-R", "name": { "family": "Wik", "given": "D. R." }, "orcid": "0000-0001-8952-676X" }, { "id": "Williams-B-F", "name": { "family": "Williams", "given": "B. F." }, "orcid": "0000-0002-7502-0597" }, { "id": "Wilms-J", "name": { "family": "Wilms", "given": "J." }, "orcid": "0000-0003-2065-5410" }, { "id": "Yukita-Mihoko", "name": { "family": "Yukita", "given": "M." }, "orcid": "0000-0001-6366-3459" }, { "id": "Zezas-A", "name": { "family": "Zezas", "given": "A." }, "orcid": "0000-0001-8952-676X" } ] }, "title": "Astro 2020 Science White Paper: Time Domain Studies of Neutron Star and Black Hole Populations: X-ray Identification of Compact Object Types", "ispublished": "unpub", "full_text_status": "public", "note": "Submitted - 1903.09858.pdf
", "abstract": "What are the most important conditions and processes governing the growth of stellar-origin compact objects? The identification of compact object type as either black hole (BH) or neutron star (NS) is fundamental to understanding their formation and evolution. To date, time-domain determination of compact object type remains a relatively untapped tool. Measurement of orbital periods, pulsations, and bursts will lead to a revolution in the study of the demographics of NS and BH populations, linking source phenomena to accretion and galaxy parameters (e.g., star formation, metallicity). To perform these measurements over sufficient parameter space, a combination of a wide-field (>5000 deg^2) transient X-ray monitor over a dynamic energy range (~1-100 keV) and an X-ray telescope for deep surveys with <5 arcsec PSF half-energy width (HEW) angular resolution are required. Synergy with multiwavelength data for characterizing the underlying stellar population will transform our understanding of the time domain properties of transient sources, helping to explain details of supernova explosions and gravitational wave event rates.", "date": "2019-03-23", "date_type": "published", "publisher": "arXiv", "id_number": "CaltechAUTHORS:20190618-092213251", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190618-092213251", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "Space-Radiation-Laboratory" } ] }, "doi": "10.48550/arXiv.1903.09858", "primary_object": { "basename": "1903.09858.pdf", "url": "https://authors.library.caltech.edu/records/079rp-w0723/files/1903.09858.pdf" }, "pub_year": "2019", "author_list": "Vulic, N.; Hornschemeier, A. E.; et al." }, { "id": "https://authors.library.caltech.edu/records/5cv6k-38w78", "eprint_id": 98681, "eprint_status": "archive", "datestamp": "2023-08-19 14:57:21", "lastmod": "2025-02-02 21:02:11", "type": "publication_whitepaper", "metadata_visibility": "show", "creators": { "items": [ { "id": "Reynolds-C-S", "name": { "family": "Reynolds", "given": "Christopher" } }, { "id": "Petre-R", "name": { "family": "Petre", "given": "Robert" } }, { "id": "Corcoran-M-F", "name": { "family": "Corcoran", "given": "Michael" } }, { "id": "Arnaud-K", "name": { "family": "Arnaud", "given": "Keith" } }, { "id": "Brandt-N", "name": { "family": "Brandt", "given": "Niel" } }, { "id": "Brenneman-L-W", "name": { "family": "Brenneman", "given": "Laura" } }, { "id": "Cornish-N-J", "name": { "family": "Cornish", "given": "Neil" } }, { "id": "Gonzales-G", "name": { "family": "Gonzales", "given": "Gabriela" } }, { "id": "Lopez-L-A", "name": { "family": "Lopez", "given": "Laura" }, "orcid": "0000-0002-1790-3148" }, { "id": "Madsen-K-K", "name": { "family": "Madsen", "given": "Kristin" }, "orcid": "0000-0003-1252-4891" } ] }, "title": "High-Energy Astrophysics in the 2020s and Beyond", "ispublished": "unpub", "full_text_status": "public", "note": "Submitted - 1903.07760.pdf
", "abstract": "With each passing decade, we gain new appreciation for the dynamic, connected, and often violent nature of the Universe. This reality necessarily places the study of high-energy processes at the very heart of modern astrophysics. This White Paper illustrates the central role of high-energy astrophysics to some of the most pressing astrophysical problems of our time, the formation/evolution of galaxies, the origin of the heavy elements, star and planet formation, the emergence of life on exoplanets, and the search for new physics. We also highlight the new connections that are growing between astrophysicists and plasma physicists. We end with a discussion of the challenges that must be addressed to realize the potential of these connections, including the need for integrated planning across physics and astronomy programs in multiple agencies, and the need to foster the creativity and career aspirations of individual scientists in this era of large projects.", "date": "2019-03-18", "date_type": "published", "publisher": "arXiv", "id_number": "CaltechAUTHORS:20190917-133815385", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190917-133815385", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "Space-Radiation-Laboratory" } ] }, "doi": "10.48550/arXiv.1903.07760", "primary_object": { "basename": "1903.07760.pdf", "url": "https://authors.library.caltech.edu/records/5cv6k-38w78/files/1903.07760.pdf" }, "pub_year": "2019", "author_list": "Reynolds, Christopher; Petre, Robert; et al." }, { "id": "https://authors.library.caltech.edu/records/byx2b-pjy19", "eprint_id": 96557, "eprint_status": "archive", "datestamp": "2023-08-19 14:56:54", "lastmod": "2025-02-02 20:58:11", "type": "publication_whitepaper", "metadata_visibility": "show", "creators": { "items": [ { "id": "Garc\u00eda-Javier-A", "name": { "family": "Garc\u00eda", "given": "Javier A." }, "orcid": "0000-0003-3828-2448" }, { "id": "Bachetti-M", "name": { "family": "Bachetti", "given": "Matteo" }, "orcid": "0000-0002-4576-9337" }, { "id": "Ballantyne-D-R", "name": { "family": "Ballantyne", "given": "David R." }, "orcid": "0000-0001-8128-6976" }, { "id": "Brenneman-L-W", "name": { "family": "Brenneman", "given": "Laura" } }, { "id": "Brightman-M", "name": { "family": "Brightman", "given": "Murray" }, "orcid": "0000-0002-8147-2602" }, { "id": "Connors-R-M-T", "name": { "family": "Connors", "given": "Riley M." }, "orcid": "0000-0002-8908-759X" }, { "id": "Dauser-T", "name": { "family": "Dauser", "given": "Thomas" }, "orcid": "0000-0003-4583-9048" }, { "id": "Fabian-A-C", "name": { "family": "Fabian", "given": "Andrew" }, "orcid": "0000-0002-9378-4072" }, { "id": "F\u00fcrst-F", "name": { "family": "Fuerst", "given": "Felix" }, "orcid": "0000-0003-0388-0560" }, { "id": "Gandhi-Poshak", "name": { "family": "Gandhi", "given": "Poshak" }, "orcid": "0000-0003-3105-2615" }, { "id": "Kamraj-N", "name": { "family": "Kamraj", "given": "Nikita" }, "orcid": "0000-0002-3233-2451" }, { "id": "Kara-E", "name": { "family": "Kara", "given": "Erin" }, "orcid": "0000-0003-0172-0854" }, { "id": "Madsen-K-K", "name": { "family": "Madsen", "given": "Kristin" }, "orcid": "0000-0003-1252-4891" }, { "id": "Miller-J-M", "name": { "family": "Miller", "given": "Jon M." } }, { "id": "Nowak-M-A", "name": { "family": "Nowak", "given": "Michael" }, "orcid": "0000-0001-6923-1315" }, { "id": "Parker-M-L", "name": { "family": "Parker", "given": "Michael L." }, "orcid": "0000-0002-8466-7317" }, { "id": "Reynolds-C-S", "name": { "family": "Reynolds", "given": "Christopher" } }, { "id": "Steiner-J-F", "name": { "family": "Steiner", "given": "James" }, "orcid": "0000-0002-5872-6061" }, { "id": "Stern-D", "name": { "family": "Stern", "given": "Daniel" }, "orcid": "0000-0003-2686-9241" }, { "id": "Taylor-C", "name": { "family": "Taylor", "given": "Corbin" } }, { "id": "Tomsick-J-A", "name": { "family": "Tomsick", "given": "John" }, "orcid": "0000-0001-5506-9855" }, { "id": "Walton-D-J", "name": { "family": "Walton", "given": "Dominic" }, "orcid": "0000-0001-5819-3552" }, { "id": "Wilms-J", "name": { "family": "Wilms", "given": "J\u00f6rn" }, "orcid": "0000-0003-2065-5410" }, { "id": "Zoghbi-A", "name": { "family": "Zoghbi", "given": "Abderahmen" }, "orcid": "0000-0002-0572-9613" } ] }, "title": "Probing the Black Hole Engine with Measurements of the Relativistic X-ray Reflection Component", "ispublished": "unpub", "full_text_status": "public", "note": "Submitted - 1903.07130.pdf
", "abstract": "Over the last decades X-ray spectroscopy has proven to be a powerful tool for the estimation of black hole spin and several other key parameters in dozens of AGN and black hole X-ray binaries. In this White Paper, we discuss the observational and theoretical challenges expected in the exploration, discovery, and study of astrophysical black holes in the next decade. We focus on the case of accreting black holes and their electromagnetic signatures, with particular emphasis on the measurement of the relativistic reflection component in their X-ray spectra.", "date": "2019-03-17", "date_type": "published", "publisher": "arXiv", "id_number": "CaltechAUTHORS:20190619-103025261", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190619-103025261", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "Space-Radiation-Laboratory" } ] }, "doi": "10.48550/arXiv.1903.07130", "primary_object": { "basename": "1903.07130.pdf", "url": "https://authors.library.caltech.edu/records/byx2b-pjy19/files/1903.07130.pdf" }, "pub_year": "2019", "author_list": "Garc\u00eda, Javier A.; Bachetti, Matteo; et al." }, { "id": "https://authors.library.caltech.edu/records/xmn7m-rrr02", "eprint_id": 96477, "eprint_status": "archive", "datestamp": "2023-08-19 14:55:49", "lastmod": "2025-02-02 20:57:46", "type": "publication_whitepaper", "metadata_visibility": "show", "creators": { "items": [ { "id": "Brightman-Murray", "name": { "family": "Brightman", "given": "M." }, "orcid": "0000-0002-8147-2602" }, { "id": "Bachetti-Matteo", "name": { "family": "Bachetti", "given": "M." }, "orcid": "0000-0002-4576-9337" }, { "id": "Earnshaw-Hannah-P", "name": { "family": "Earnshaw", "given": "H. P." }, "orcid": "0000-0001-5857-5622" }, { "id": "F\u00fcrst-Felix", "name": { "family": "F\u00fcrst", "given": "F." }, "orcid": "0000-0003-0388-0560" }, { "id": "Garc\u00eda-Javier-A", "name": { "family": "Garc\u00eda", "given": "J." }, "orcid": "0000-0003-3828-2448" }, { "id": "Grefenstette-Brian-W", "name": { "family": "Grefenstette", "given": "B." }, "orcid": "0000-0002-1984-2932" }, { "id": "Heida-Marianne", "name": { "family": "Heida", "given": "M." }, "orcid": "0000-0002-1082-7496" }, { "id": "Kara-Erin", "name": { "family": "Kara", "given": "E." }, "orcid": "0000-0003-0172-0854" }, { "id": "Madsen-Kristin-K", "name": { "family": "Madsen", "given": "K. K." }, "orcid": "0000-0003-1252-4891" }, { "id": "Middleton-Matthew-J", "name": { "family": "Middleton", "given": "M. J." }, "orcid": "0000-0002-8183-2970" }, { "id": "Stern-Daniel", "name": { "family": "Stern", "given": "D." }, "orcid": "0000-0003-2686-9241" }, { "id": "Tombesi-Francesco", "name": { "family": "Tombesi", "given": "F." }, "orcid": "0000-0002-6562-8654" }, { "id": "Walton-Dominic-J", "name": { "family": "Walton", "given": "D. J." }, "orcid": "0000-0001-5819-3552" } ] }, "title": "Breaking the limit: Super-Eddington accretion onto black holes and neutron stars", "ispublished": "unpub", "full_text_status": "public", "note": "Submitted - 1903.06844.pdf
", "abstract": "With the recent discoveries of massive and highly luminous quasars at high redshifts (z\u223c7; e.g. Mortlock et al. 2011), the question of how black holes (BHs) grow in the early Universe has been cast in a new light. In order to grow BHs with M_(BH) > 10^9 M\u2299 by less than a billion years after the Big Bang, mass accretion onto the low-mass seed BHs needs to have been very rapid (Volonteri & Rees, 2005). Indeed, for any stellar remnant seed, the rate required would need to exceed the Eddington limit. This is the point at which the outward force produced by radiation pressure is equal to the gravitational attraction experienced by the in-falling matter. In principle, this implies that there is a maximum luminosity an object of mass M can emit; assuming spherical accretion and that the opacity is dominated by Thompson scattering, this Eddington luminosity is L_E = 1.38\u00d710^(38)(M/M\u2299) erg s^(\u22121). In reality, it is known that this limit can be violated, due to non-spherical geometry or various kinds of instabilities. Nevertheless, the Eddington limit remains an important reference point, and many of the details of how accretion proceeds above this limit remain unclear. Understanding how this so-called super-Eddington accretion occurs is of clear cosmological importance, since it potentially governs the growth of the first supermassive black holes (SMBHs) and the impact this growth would have had on their host galaxies ('feedback') and the epoch of reionization, as well as improving our understanding of accretion physics more generally.", "date": "2019-03-15", "date_type": "published", "publisher": "arXiv", "id_number": "CaltechAUTHORS:20190617-141021193", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190617-141021193", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "Space-Radiation-Laboratory" } ] }, "doi": "10.48550/arXiv.1903.06844", "primary_object": { "basename": "1903.06844.pdf", "url": "https://authors.library.caltech.edu/records/xmn7m-rrr02/files/1903.06844.pdf" }, "pub_year": "2019", "author_list": "Brightman, M.; Bachetti, M.; et al." }, { "id": "https://authors.library.caltech.edu/records/3zamc-51v78", "eprint_id": 98682, "eprint_status": "archive", "datestamp": "2023-08-19 14:51:28", "lastmod": "2025-02-02 21:02:14", "type": "publication_whitepaper", "metadata_visibility": "show", "creators": { "items": [ { "id": "Kamraj-N", "name": { "family": "Kamraj", "given": "Nikita" }, "orcid": "0000-0002-3233-2451" }, { "id": "Fabian-A-C", "name": { "family": "Fabian", "given": "Andrew" }, "orcid": "0000-0002-9378-4072" }, { "id": "Lohfink-A-M", "name": { "family": "Lohfink", "given": "Anne" } }, { "id": "Balokovi\u0107-M", "name": { "family": "Balokovi\u0107", "given": "Mislav" }, "orcid": "0000-0003-0476-6647" }, { "id": "Ricci-C", "name": { "family": "Ricci", "given": "Claudio" }, "orcid": "0000-0001-5231-2645" }, { "id": "Madsen-K-K", "name": { "family": "Madsen", "given": "Kristin" }, "orcid": "0000-0003-1252-4891" } ] }, "title": "Probing the Physical Properties of the Corona in Accreting Black Holes", "ispublished": "unpub", "full_text_status": "public", "keywords": "Formation and Evolution of Compact Objects, Galaxy Evolution", "note": "Submitted - 1903.05241.pdf
", "abstract": "The corona is a key component of most luminous accreting black holes, carrying 5 - 30 % of the power and in non-jetted Active Galactic Nuclei (AGN), creating all the X-ray emission above \u22431\u22122 keV. Its emission illuminates the inner accretion disc, creating the atomic line-rich reflection spectrum used to diagnose and map the accretion flow and measure black hole spin. The corona is likely powered magnetically by the strong differential rotation of the accretion disc and it may be intimately related to relativistic jets. Recent work shows that many black hole coronae may be dominated by electron-positron pairs produced by photon-photon collisions in the compact coronal environment. Despite the corona being an integral component of AGN and black hole binary systems, much is still unknown about the nature of the corona, such as its geometry, location, and the physical mechanisms powering the emission. In this white paper we explore our current understanding of coronal properties, such as its temperature, obtained from measurements with existing hard X-ray telescopes such as NuSTAR, and discuss important questions to be addressed in the coming decade surrounding the nature of the corona. Hard X-ray observations will continue to dispel the mystery of coronae and open up this part of the quasar engine to full understanding.", "date": "2019-03-12", "date_type": "published", "publisher": "arXiv", "id_number": "CaltechAUTHORS:20190917-134419227", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190917-134419227", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "Space-Radiation-Laboratory" } ] }, "doi": "10.48550/arXiv.1903.05241", "primary_object": { "basename": "1903.05241.pdf", "url": "https://authors.library.caltech.edu/records/3zamc-51v78/files/1903.05241.pdf" }, "pub_year": "2019", "author_list": "Kamraj, Nikita; Fabian, Andrew; et al." }, { "id": "https://authors.library.caltech.edu/records/dgec5-qdf76", "eprint_id": 101099, "eprint_status": "archive", "datestamp": "2023-08-19 14:50:35", "lastmod": "2025-02-02 21:03:41", "type": "publication_whitepaper", "metadata_visibility": "show", "creators": { "items": [ { "id": "Fields-B-D", "name": { "family": "Fields", "given": "Brian D." } }, { "id": "Mewaldt-R-A", "name": { "family": "Mewaldt", "given": "Richard A." }, "orcid": "0000-0003-2178-9111" } ] }, "title": "Near-Earth Supernova Explosions: Evidence, Implications, and Opportunities", "ispublished": "unpub", "full_text_status": "public", "note": "Astro2020 Science White Paper submitted to the 2020 Decadal Survey on Astronomy and Astrophysics.\n\nSubmitted - 1903.04589.pdf
", "abstract": "There is now solid experimental evidence of at least one supernova explosion within 100 pc of Earth within the last few million years, from measurements of the short-lived isotope \u2076\u2070Fe in widespread deep-ocean samples, as well as in the lunar regolith and cosmic rays. This is the first established example of a specific dated astrophysical event outside the Solar System having a measurable impact on the Earth, offering new probes of stellar evolution, nuclear astrophysics, the astrophysics of the solar neighborhood, cosmic-ray sources and acceleration, multi-messenger astronomy, and astrobiology. Interdisciplinary connections reach broadly to include heliophysics, geology, and evolutionary biology. Objectives for the future include pinning down the nature and location of the established near-Earth supernova explosions, seeking evidence for others, and searching for other short-lived isotopes such as \u00b2\u2076Al and \u00b2\u2074\u2074Pu. The unique information provided by geological and lunar detections of radioactive \u2076\u2070Fe to assess nearby supernova explosions make now a compelling time for the astronomy community to advocate for supporting multi-disciplinary, cross-cutting research programs.", "date": "2019-03-11", "date_type": "published", "id_number": "CaltechAUTHORS:20200204-081236612", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200204-081236612", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "Space-Radiation-Laboratory" } ] }, "doi": "10.48550/arXiv.1903.04589", "primary_object": { "basename": "1903.04589.pdf", "url": "https://authors.library.caltech.edu/records/dgec5-qdf76/files/1903.04589.pdf" }, "pub_year": "2019", "author_list": "Fields, Brian D. and Mewaldt, Richard A." }, { "id": "https://authors.library.caltech.edu/records/z0k54-jzg77", "eprint_id": 98675, "eprint_status": "archive", "datestamp": "2023-08-19 14:46:37", "lastmod": "2025-02-02 20:59:14", "type": "publication_whitepaper", "metadata_visibility": "show", "creators": { "items": [ { "id": "Ray-P-S", "name": { "family": "Ray", "given": "Paul S." }, "orcid": "0000-0002-5297-5278" }, { "id": "F\u00fcrst-F", "name": { "family": "Fuerst", "given": "Felix" }, "orcid": "0000-0003-0388-0560" }, { "id": "Grefenstette-B-W", "name": { "family": "Grefenstette", "given": "Brian" }, "orcid": "0000-0002-1984-2932" } ] }, "title": "STROBE-X: X-ray Timing and Spectroscopy on Dynamical Timescales from Microseconds to Years", "ispublished": "unpub", "full_text_status": "public", "note": "The STROBE-X mission concept study is funded by the NASA Astrophysics Probes program (16-APROBES16-0008). The Italian authors acknowledge support from ASI, under agreement ASI-INAF n.2017-14-H.O, INAF and INFN. The Spanish authors acknowledge support from MINECO grant ESP2017-82674-R and FEDER funds. A.L.S. is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1801792. A.L.W. acknowledges support from ERC Starting Grant 639217. \n\nWe gratefully acknowledge the superb engineering teams at the NASA/GSFC Instrument Design Lab and Mission Design Lab, Steve Kenyon, and Takashi Okajima, for their important contributions\nto the STROBE-X technical concept. We thank Lorenzo Amati and Giulia Stratta for useful discussions.\n\nSubmitted - 1903.03035.pdf
", "abstract": "We present the Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays (STROBE-X), a probe-class mission concept selected for study by NASA. It combines huge collecting area, high throughput, broad energy coverage, and excellent spectral and temporal resolution in a single facility. STROBE-X offers an enormous increase in sensitivity for X-ray spectral timing, extending these techniques to extragalactic targets for the first time. It is also an agile mission capable of rapid response to transient events, making it an essential X-ray partner facility in the era of time-domain, multi-wavelength, and multi-messenger astronomy. Optimized for study of the most extreme conditions found in the Universe, its key science objectives include: (1) Robustly measuring mass and spin and mapping inner accretion flows across the black hole mass spectrum, from compact stars to intermediate-mass objects to active galactic nuclei. (2) Mapping out the full mass-radius relation of neutron stars using an ensemble of nearly two dozen rotation-powered pulsars and accreting neutron stars, and hence measuring the equation of state for ultradense matter over a much wider range of densities than explored by NICER. (3) Identifying and studying X-ray counterparts (in the post-Swift era) for multiwavelength and multi-messenger transients in the dynamic sky through cross-correlation with gravitational wave interferometers, neutrino observatories, and high-cadence time-domain surveys in other electromagnetic bands. (4) Continuously surveying the dynamic X-ray sky with a large duty cycle and high time resolution to characterize the behavior of X-ray sources over an unprecedentedly vast range of time scales. STROBE-X's formidable capabilities will also enable a broad portfolio of additional science.", "date": "2019-03-07", "date_type": "published", "id_number": "CaltechAUTHORS:20190917-110443914", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190917-110443914", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NASA", "grant_number": "16-APROBES16-0008" }, { "agency": "Agenzia Spaziale Italiana (ASI)", "grant_number": "2017-14-H.0" }, { "agency": "Istituto Nazionale di Astrofisica (INAF)" }, { "agency": "Istituto Nazionale di Fisica Nucleare (INFN)" }, { "agency": "Ministerio de Econom\u00eda, Industria y Competitividad (MINECO)", "grant_number": "ESP2017-82674-R" }, { "agency": "Fondo Europeo de Desarrollo Regional (FEDER)" }, { "agency": "NSF Astronomy and Astrophysics Fellowship", "grant_number": "AST-1801792" }, { "agency": "European Research Council (ERC)", "grant_number": "639217" } ] }, "local_group": { "items": [ { "id": "Space-Radiation-Laboratory" } ] }, "doi": "10.48550/arXiv.1903.03035", "primary_object": { "basename": "1903.03035.pdf", "url": "https://authors.library.caltech.edu/records/z0k54-jzg77/files/1903.03035.pdf" }, "pub_year": "2019", "author_list": "Ray, Paul S.; Fuerst, Felix; et al." }, { "id": "https://authors.library.caltech.edu/records/j4bnz-h8464", "eprint_id": 98680, "eprint_status": "archive", "datestamp": "2023-08-19 14:15:59", "lastmod": "2025-06-30 18:18:50", "type": "publication_whitepaper", "metadata_visibility": "show", "creators": { "items": [ { "id": "Fryer-C-L", "name": { "family": "Fryer", "given": "Chris L." }, "orcid": "0000-0003-2624-0056" }, { "id": "Grefenstette-B-W", "name": { "family": "Grefenstette", "given": "Brian" }, "orcid": "0000-0002-1984-2932" }, { "id": "Harrison-F-A", "name": { "family": "Harrison", "given": "Fiona" }, "orcid": "0000-0002-4226-8959" }, { "id": "Madsen-K-K", "name": { "family": "Madsen", "given": "Kristin" }, "orcid": "0000-0003-1252-4891" } ] }, "title": "Catching Element Formation In The Act - The Case for a New MeV Gamma-Ray Mission: Radionuclide Astronomy in the 2020s", "ispublished": "unpub", "full_text_status": "public", "note": "A White Paper for the 2020 Decadal Survey.\n\nSubmitted - 1902.02915.pdf
", "abstract": "Gamma-ray astronomy explores the most energetic photons in nature to address some of the most pressing puzzles in contemporary astrophysics. It encompasses a wide range of objects and phenomena: stars, supernovae, novae, neutron stars, stellar-mass black holes, nucleosynthesis, the interstellar medium, cosmic rays and relativistic-particle acceleration, and the evolution of galaxies. MeV gamma-rays provide a unique probe of nuclear processes in astronomy, directly measuring radioactive decay, nuclear de-excitation, and positron annihilation. The substantial information carried by gamma-ray photons allows us to see deeper into these objects, the bulk of the power is often emitted at gamma-ray energies, and radioactivity provides a natural physical clock that adds unique information. New science will be driven by time-domain population studies at gamma-ray energies. This science is enabled by next-generation gamma-ray instruments with one to two orders of magnitude better sensitivity, larger sky coverage, and faster cadence than all previous gamma-ray instruments. This transformative capability permits: (a) the accurate identification of the gamma-ray emitting objects and correlations with observations taken at other wavelengths and with other messengers; (b) construction of new gamma-ray maps of the Milky Way and other nearby galaxies where extended regions are distinguished from point sources; and (c) considerable serendipitous science of scarce events -- nearby neutron star mergers, for example. Advances in technology push the performance of new gamma-ray instruments to address a wide set of astrophysical questions.", "date": "2019-02-08", "date_type": "published", "id_number": "CaltechAUTHORS:20190917-133401954", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190917-133401954", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "Space-Radiation-Laboratory" }, { "id": "Astronomy-Department" } ] }, "doi": "10.48550/arXiv.1902.02915", "primary_object": { "basename": "1902.02915.pdf", "url": "https://authors.library.caltech.edu/records/j4bnz-h8464/files/1902.02915.pdf" }, "pub_year": "2019", "author_list": "Fryer, Chris L.; Grefenstette, Brian; et al." } ]