Journal article · Preprint article
The NuSTAR Hard X-Ray Survey of the Norma Arm Region
University of California at Berkeley1
National Space Institute, Technical University of Denmark2
Astrophysics and Atmospheric Physics, National Space Institute, Technical University of Denmark3
Lawrence Livermore National Laboratory4
ASI Science Data Center5
Hiroshima University6
SLAC National Accelerator Laboratory7
National Institute for Astrophysics8
NASA Goddard Space Flight Center9
Harvard-Smithsonian Center for Astrophysics10
Columbia University11
Pontificia Universidad Católica de Chile12
European Southern Observatory13
California Institute of Technology14
Georgia College & State University15
Durham University16
Université Fédérale Toulouse Midi-Pyrénées17
...and 7 moreWe 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.
Language: | English |
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Publisher: | American Astronomical Society |
Year: | 2017 |
Pages: | 33 |
ISSN: | 15384365 and 00670049 |
Types: | Journal article and Preprint article |
DOI: | 10.3847/1538-4365/aa61fc |
ORCIDs: | Christensen, Finn Erland , Hornstrup, Allan , Westergaard, Niels Jørgen Stenfeldt , 0000-0002-9286-9963 , 0000-0001-5506-9855 , 0000-0003-3847-3957 , 0000-0002-8686-8737 , 0000-0001-7655-4120 , 0000-0003-2686-9241 , 0000-0002-7315-3732 , 0000-0003-2737-5673 , 0000-0002-9709-5389 , 0000-0002-5896-6313 , 0000-0002-0393-9190 , 0000-0002-1984-2932 , 0000-0003-2992-8024 , 0000-0003-1252-4891 , 0000-0002-8074-4186 , 0000-0002-2734-7835 and 0000-0003-1703-8796 |