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dc.contributor.authorBarillier, Erin
dc.contributor.authorGrinberg, Victoria
dc.contributor.authorHorn, David
dc.contributor.authorNowak, Michael A.
dc.contributor.authorRemillard, Ronald A.
dc.contributor.authorSteiner, James F.
dc.contributor.authorWalton, Dominic J.
dc.contributor.authorWilms, Jörn
dc.date.accessioned2023-02-23T17:15:01Z
dc.date.available2023-02-23T17:15:01Z
dc.date.issued2023-02-22
dc.identifier.citationBarillier , E , Grinberg , V , Horn , D , Nowak , M A , Remillard , R A , Steiner , J F , Walton , D J & Wilms , J 2023 , ' NICER/NuSTAR Characterization of 4U 1957+11: A Near Maximally Spinning Black Hole Potentially in the Mass Gap ' , The Astrophysical Journal , vol. 944 , no. 2 , 165 , pp. 1-16 . https://doi.org/10.3847/1538-4357/acaeaf
dc.identifier.issn0004-637X
dc.identifier.otherArXiv: http://arxiv.org/abs/2301.09226v1
dc.identifier.otherJisc: 917482
dc.identifier.otherpublisher-id: apjacaeaf
dc.identifier.othermanuscript: acaeaf
dc.identifier.otherother: aas42905
dc.identifier.otherORCID: /0000-0001-5819-3552/work/129622121
dc.identifier.urihttp://hdl.handle.net/2299/26087
dc.description© 2023. The Author(s). Published by the American Astronomical Society. This is an open access article distributed under the Creative Commons Attribution License, to view a copy of the license, see: https://creativecommons.org/licenses/by/4.0/
dc.description.abstract4U 1957+11 is a black hole candidate system that has been in a soft X-ray spectral state since its discovery. We present analyses of recent joint NICER and NuSTAR spectra, which are extremely well described by a highly inclined disk accreting into a near maximally spinning black hole. Owing to the broad X-ray coverage of NuSTAR, the fitted spin and inclination are strongly constrained for our hypothesized disk models. The faintest spectra are observed out to 20 keV, even though their hard tail components are almost absent when described with a simple corona. The hard tail increases with luminosity, but shows clear two-track behavior with one track having appreciably stronger tails. The disk spectrum color-correction factor is anticorrelated with the strength of the hard tail (e.g., as measured by the Compton y parameter). Although the spin and inclination parameters are strongly constrained for our chosen model, the mass and distance are degenerate parameters. We use our spectral fits, along with a theoretical prior on color-correction, an observational prior on likely fractional Eddington luminosity, and an observational prior on distance obtained from Gaia studies, to present mass and distance contours for this system. The most likely parameters, given our presumed disk model, suggest a 4.6 M ⊙ black hole at 7.8 kpc observed at luminosities ranging from ≈1.7% to 9% of Eddington. This would place 4U 1957+11 as one of the few actively accreting sources within the mass gap of ≈2–5 M ⊙ where there are few known massive neutron stars or low-mass black holes. Higher mass and distance, however, remain viable.en
dc.format.extent16
dc.format.extent7933955
dc.language.isoeng
dc.relation.ispartofThe Astrophysical Journal
dc.subject330
dc.subjectHigh-Energy Phenomena and Fundamental Physics
dc.subjectAstronomy and Astrophysics
dc.subjectSpace and Planetary Science
dc.titleNICER/NuSTAR Characterization of 4U 1957+11: A Near Maximally Spinning Black Hole Potentially in the Mass Gapen
dc.contributor.institutionCentre for Astrophysics Research
dc.contributor.institutionDepartment of Physics, Astronomy and Mathematics
dc.contributor.institutionSchool of Physics, Engineering & Computer Science
dc.description.statusPeer reviewed
dc.identifier.urlhttp://www.scopus.com/inward/record.url?scp=85148871536&partnerID=8YFLogxK
rioxxterms.versionofrecord10.3847/1538-4357/acaeaf
rioxxterms.typeJournal Article/Review
herts.preservation.rarelyaccessedtrue


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