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

Hong, JaeSub; Mori, Kaya; Hailey, Charles J.; Nynka, Melania; Zhang, Shuo; Gotthelf, Eric; Fornasini, Francesca M.; Krivonos, Roman; Bauer, Franz; Perez, Kerstin; Tomsick, John A.; Bodaghee, Arash; Chiu, Jeng-Lun; Clavel, Maïca; Stern, Daniel; Grindlay, Jonathan E.; Alexander, David M.; Aramaki, Tsuguo; Baganoff, Frederick K.; Barret, Didier; Barrière, Nicolas; Boggs, Steven E.; Canipe, Alicia M.; Christensen, Finn E.; Craig, William W.; Desai, Meera A.; Forster, Karl; Giommi, Paolo; Grefenstette, Brian W.; Harrison, Fiona A.; Hong, Dooran; Hornstrup, Allan; Kitaguchi, Takao; Koglin, Jason E.; Madsen, Kristen K.; Mao, Peter H.; Miyasaka, Hiromasa; Perri, Matteo; Pivovaroff, Michael J.; Puccetti, Simonetta; Rana, Vikram; Westergaard, Niels J.; Zhang, William W.; Zoglauer, Andreas

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


Authors

JaeSub Hong

Kaya Mori

Charles J. Hailey

Melania Nynka

Shuo Zhang

Eric Gotthelf

Francesca M. Fornasini

Roman Krivonos

Franz Bauer

Kerstin Perez

John A. Tomsick

Arash Bodaghee

Jeng-Lun Chiu

Maïca Clavel

Daniel Stern

Jonathan E. Grindlay

Tsuguo Aramaki

Frederick K. Baganoff

Didier Barret

Nicolas Barrière

Steven E. Boggs

Alicia M. Canipe

Finn E. Christensen

William W. Craig

Meera A. Desai

Karl Forster

Paolo Giommi

Brian W. Grefenstette

Fiona A. Harrison

Dooran Hong

Allan Hornstrup

Takao Kitaguchi

Jason E. Koglin

Kristen K. Madsen

Peter H. Mao

Hiromasa Miyasaka

Matteo Perri

Michael J. Pivovaroff

Simonetta Puccetti

Vikram Rana

Niels J. Westergaard

William W. Zhang

Andreas Zoglauer



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.

Journal Article Type Article
Acceptance Date May 12, 2016
Online Publication Date Jul 12, 2016
Publication Date Jul 12, 2016
Deposit Date Jun 21, 2017
Publicly Available Date Jul 3, 2017
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 825
Issue 2
Article Number 132
DOI https://doi.org/10.3847/0004-637x/825/2/132
Public URL https://durham-repository.worktribe.com/output/1356675

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Copyright Statement
© 2016. The American Astronomical Society. All rights reserved.






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