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Galactic Sources Detected in the NuSTAR Serendipitous Survey

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posted on 2018-08-10, 11:03 authored by John A. Tomsick, George B. Lansbury, Farid Rahoui, Maïca Clavel, Francesca M. Fornasini, JaeSub Hong, James Aird, David M. Alexander, 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 deg$^2$ 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.


This work made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. We thank the NuSTAR Operations, Software and Calibration teams for support with the execution and analysis of these observations. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA). Data from Swift, XMM, and Chandra were also used, and the work on serendipitous NuSTAR sources is partially funded by Chandra grants GO5-16154X and GO6-17135X. R.K. acknowledges support from Russian Science Foundation (grant 14-12-01315). We acknowledge useful discussions with A. Shaw, and we thank the referee for helpful comments. This work has made use of data from the European Space Agency (ESA) mission Gaia, 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. This research had made use of the SIMBAD database and the VizieR catalog access tool, CDS, Strasbourg, France.



Astrophysical Journal Supplement, 2017, 230, pp. 25-25

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/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy


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