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Galactic Sources Detected in the NuSTAR Serendipitous Survey

Tomsick, John A.; Lansbury, George B.; Rahoui, Farid; Clavel, Maïca; Fornasini, Francesca M.; Hong, JaeSub; Aird, James; Alexander, David M.; Bodaghee, Arash; Chiu, Jeng-Lun; Grindlay, Jonathan E.; Hailey, Charles J.; Harrison, Fiona A.; Krivonos, Roman A.; Mori, Kaya; Stern, Daniel

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John A. Tomsick

George B. Lansbury

Farid Rahoui

Maïca Clavel

Francesca M. Fornasini

JaeSub Hong

James Aird

Arash Bodaghee

Jeng-Lun Chiu

Jonathan E. Grindlay

Charles J. Hailey

Fiona A. Harrison

Roman A. Krivonos

Kaya Mori

Daniel Stern


The Nuclear Spectroscopic Telescope Array (NuSTAR) provides an improvement in sensitivity at energies above 10 keV by two orders of magnitude over non-focusing satellites, making it possible to probe deeper into the Galaxy and universe. Lansbury and collaborators recently completed a catalog of 497 sources serendipitously detected in the 3–24 keV band using 13 deg2 of NuSTAR coverage. Here, we report on an optical and X-ray study of 16 Galactic sources in the catalog. We identify 8 of them as stars (but some or all could have binary companions), and use information from Gaia to report distances and X-ray luminosities for 3 of them. There are 4 CVs or CV candidates, and we argue that NuSTAR J233426–2343.9 is a relatively strong CV candidate based partly on an X-ray spectrum from XMM-Newton. NuSTAR J092418–3142.2, which is the brightest serendipitous source in the Lansbury catalog, and NuSTAR J073959–3147.8 are low-mass X-ray binary candidates, but it is also possible that these 2 sources are CVs. One of the sources is a known high-mass X-ray binary (HMXB), and NuSTAR J105008–5958.8 is a new HMXB candidate that has strong Balmer emission lines in its optical spectrum and a hard X-ray spectrum. We discuss the implications of finding these HMXBs for the surface density (log N–log S) and luminosity function of Galactic HMXBs. We conclude that with the large fraction of unclassified sources in the Galactic plane detected by NuSTAR in the 8–24 keV band, there could be a significant population of low-luminosity HMXBs.

Journal Article Type Article
Acceptance Date May 23, 2017
Online Publication Date Jun 23, 2017
Publication Date Jun 23, 2017
Deposit Date Jul 13, 2017
Publicly Available Date Jul 13, 2017
Journal Astrophysical Journal Supplement
Print ISSN 0067-0049
Electronic ISSN 1538-4365
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 230
Issue 2
Article Number 25
Public URL


Published Journal Article (1.8 Mb)

Copyright Statement
© 2017. The American Astronomical Society. All rights reserved.

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