The NuSTAR Hard X-Ray Survey of the Norma Arm Region
Date Issued
2017
Author(s)
Fornasini, Francesca M.
•
Tomsick, John A.
•
Hong, JaeSub
•
Gotthelf, Eric V.
•
Bauer, Franz
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Rahoui, Farid
•
Stern, Daniel
•
Bodaghee, Arash
•
Chiu, Jeng-Lun
•
Clavel, Maïca
•
Corral-Santana, Jesús
•
Hailey, Charles J.
•
Krivonos, Roman A.
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Mori, Kaya
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Alexander, David M.
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Barret, Didier
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Boggs, Steven E.
•
Christensen, Finn E.
•
Craig, William W.
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Forster, Karl
•
Giommi, Paolo
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Grefenstette, Brian W.
•
Harrison, Fiona A.
•
Hornstrup, Allan
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Kitaguchi, Takao
•
Koglin, J. E.
•
Madsen, Kristin K.
•
Mao, Peter H.
•
Miyasaka, Hiromasa
•
•
Pivovaroff, Michael J.
•
Puccetti, Simonetta
•
Rana, Vikram
•
Westergaard, Niels J.
•
Zhang, William W.
Abstract
We present a catalog of hard X-ray sources in a square-degree region surveyed by the Nuclear Spectroscopic Telescope Array (NuSTAR) in the direction of the Norma spiral arm. This survey has a total exposure time of 1.7 Ms, and the typical and maximum exposure depths are 50 ks and 1 Ms, respectively. In the area of deepest coverage, sensitivity limits of 5 × 10^-14 and 4 × 10^-14 erg s^-1 cm^-2 in the 3-10 and 10-20 keV bands, respectively, are reached. Twenty-eight sources are firmly detected, and 10 are detected with low significance; 8 of the 38 sources are expected to be active galactic nuclei. The three brightest sources were previously identified as a low-mass X-ray binary, high-mass X-ray binary, and pulsar wind nebula. Based on their X-ray properties and multiwavelength counterparts, we identify the likely nature of the other sources as two colliding wind binaries, three pulsar wind nebulae, a black hole binary, and a plurality of cataclysmic variables (CVs). The CV candidates in the Norma region have plasma temperatures of ≈10-20 keV, consistent with the Galactic ridge X-ray emission spectrum but lower than the temperatures of CVs near the Galactic center. This temperature difference may indicate that the Norma region has a lower fraction of intermediate polars relative to other types of CVs compared to the Galactic center. The NuSTAR logN-logS distribution in the 10-20 keV band is consistent with the distribution measured by Chandra at 2-10 keV if the average source spectrum is assumed to be a thermal model with kT ≈ 15 keV, as observed for the CV candidates.
Volume
229
Issue
2
Start page
33
Issn Identifier
0067-0049
Ads BibCode
2017ApJS..229...33F
Rights
open.access
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