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NuSTAR Hard X-Ray Survey of the Galactic Center Region. II. X-Ray Point Sources

Hong, JaeSub and Mori, Kaya and Hailey, Charles J. and Nynka, Melania and Zhang, Shuo and Gotthelf, Eric and Fornasini, Francesca M. and Krivonos, Roman and Bauer, Franz and Perez, Kerstin and Tomsick, John A. and Bodaghee, Arash and Chiu, Jeng-Lun and Clavel, Maïca and Stern, Daniel and Grindlay, Jonathan E. and Alexander, David M. and Aramaki, Tsuguo and Baganoff, Frederick K. and Barret, Didier and Barrière, Nicolas and Boggs, Steven E. and Canipe, Alicia M. and Christensen, Finn E. and Craig, William W. and Desai, Meera A. and Forster, Karl and Giommi, Paolo and Grefenstette, Brian W. and Harrison, Fiona A. and Hong, Dooran and Hornstrup, Allan and Kitaguchi, Takao and Koglin, Jason E. and Madsen, Kristin K. and Mao, Peter H. and Miyasaka, Hiromasa and Perri, Matteo and Pivovaroff, Michael J. and Puccetti, Simonetta and Rana, Vikram and Westergaard, Niels J. and Zhang, William W. and Zoglauer, Andreas (2016) NuSTAR Hard X-Ray Survey of the Galactic Center Region. II. X-Ray Point Sources. Astrophysical Journal, 825 (2). Art. No. 132. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20160805-103318852

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Abstract

We present the first survey results of hard X-ray point sources in the Galactic Center (GC) region by NuSTAR. We have discovered 70 hard (3–79 keV) X-ray point sources in a 0.6 deg^2 region around Sgr A* with a total exposure of 1.7 Ms, and 7 sources in the Sgr B2 field with 300 ks. We identify clear Chandra counterparts for 58 NuSTAR sources and assign candidate counterparts for the remaining 19. The NuSTAR survey reaches X-ray luminosities of ∼4× and ∼8 × 10^(32) erg s^(-1) at the GC (8 kpc) in the 3–10 and 10–40 keV bands, respectively. The source list includes three persistent luminous X-ray binaries (XBs) and the likely run-away pulsar called the Cannonball. New source-detection significance maps reveal a cluster of hard (> 10 keV) X-ray sources near the Sgr A diffuse complex with no clear soft X-ray counterparts. The severe extinction observed in the Chandra spectra indicates that all the NuSTAR sources are in the central bulge or are of extragalactic origin. Spectral analysis of relatively bright NuSTAR sources suggests that magnetic cataclysmic variables constitute a large fraction (> 40%–60%). Both spectral analysis and logN–logS distributions of the NuSTAR sources indicate that the X-ray spectra of the NuSTAR sources should have kT > 20 keV on average for a single temperature thermal plasma model or an average photon index of Γ = 1.5–2 for a power-law model. These findings suggest that the GC X-ray source population may contain a larger fraction of XBs with high plasma temperatures than the field population.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.3847/0004-637X/825/2/132DOIArticle
http://iopscience.iop.org/article/10.3847/0004-637X/825/2/132/pdfPublisherArticle
http://arxiv.org/abs/1605.03882arXivDiscussion Paper
ORCID:
AuthorORCID
Mori, Kaya0000-0002-9709-5389
Krivonos, Roman0000-0003-2737-5673
Bauer, Franz0000-0002-8686-8737
Stern, Daniel0000-0003-2686-9241
Alexander, David M.0000-0002-5896-6313
Boggs, Steven E.0000-0001-9567-4224
Harrison, Fiona A.0000-0003-2992-8024
Madsen, Kristin K.0000-0003-1252-4891
Puccetti, Simonetta0000-0002-2734-7835
Rana, Vikram0000-0003-1703-8796
Additional Information:© 2016. The American Astronomical Society. Received 2016 January 29. Accepted 2016 May 12. Published 2016 July 12. This work was supported under NASA Contract No. NNG08FD60C, and 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. We thank G. Ponti for careful reading and suggestions of the manuscript. 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). J. Hong acknowledges support from NASA/APRA grant NNX14AD59G. R. Krivonos acknowledges support from Russian Science Foundation through grant 14-22-00271. F.E. Bauer acknowledges support from CONICYT-Chile (Basal-CATA PFB-06/2007, FONDECYT 1141218, "EMBIGGEN" Anillo ACT1101), and the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. S. Zhang is supported by NASA Headquarters under the NASA Earth and Space Science Fellowship Program—Grant NNX13AM31. D. Barret acknowledges support from the French Space Agency (CNES).
Group:Space Radiation Laboratory, NuSTAR
Funders:
Funding AgencyGrant Number
NASANNG08FD60C
NASA/JPL/CaltechUNSPECIFIED
NASANNX14AD59G
Russian Science Foundation14-22-00271
Basal-CATAPFB-06/2007
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1141218
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)ACT1101
Iniciativa Científica Milenio del Ministerio de Economía, Fomento y TurismoIC120009
NASA Earth and Space Science FellowshipNNX13AM31
Centre National d'Études Spatiales (CNES)UNSPECIFIED
Subject Keywords:Galaxy: center; X-rays: binaries; X-rays: diffuse background; X-rays: general
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2016-44
Record Number:CaltechAUTHORS:20160805-103318852
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20160805-103318852
Official Citation:JaeSub Hong et al 2016 ApJ 825 132
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:69472
Collection:CaltechAUTHORS
Deposited By: Deborah Miles
Deposited On:10 Aug 2016 17:27
Last Modified:31 Oct 2017 20:48

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