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Title: The NuSTAR Hard X-Ray Survey of the Norma Arm Region

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{sup −14} and 4 × 10{sup −14} erg s{sup −1} cm{sup −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 regionmore » has a lower fraction of intermediate polars relative to other types of CVs compared to the Galactic center. The NuSTAR log N –log S 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.« less

Authors:
 [1]; ; ; ; ; ;  [2];  [3]; ; ;  [4]; ;  [5];  [6];  [7];  [8];  [9];  [10];  [11];  [12] more »; « less
  1. Astronomy Department, University of California, 601 Campbell Hall, Berkeley, CA 94720 (United States)
  2. Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720 (United States)
  3. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
  4. Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States)
  5. Instituto de Astrofísica and Centro de Astroingeniería, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22 (Chile)
  6. European Southern Observatory, K. Schwarzschild-Strasse 2, D-85748 Garching bei München (Germany)
  7. Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)
  8. Georgia College, 231 W. Hancock Street, Milledgeville, GA 31061 (United States)
  9. Centre for Extragalactic Astronomy, Department of Physics, Durham University, Durham, DH1 3LE (United Kingdom)
  10. Université de Toulouse, UPS-OMP, IRAP, Toulouse (France)
  11. (France)
  12. DTU Space—National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark)
Publication Date:
OSTI Identifier:
22661128
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal, Supplement Series; Journal Volume: 229; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BLACK HOLES; CATALOGS; COMPARATIVE EVALUATIONS; COSMIC X-RAY SOURCES; ELECTRON TEMPERATURE; EMISSION SPECTRA; GALAXIES; GALAXY NUCLEI; HARD X RADIATION; ION TEMPERATURE; KEV RANGE; NEBULAE; NOVAE; PLASMA; PULSARS; SENSITIVITY; TELESCOPES

Citation Formats

Fornasini, Francesca M., Tomsick, John A., Chiu, Jeng-Lun, Clavel, Maïca, Krivonos, Roman A., Boggs, Steven E., Craig, William W., Hong, JaeSub, Gotthelf, Eric V., Hailey, Charles J., Mori, Kaya, Bauer, Franz, Corral-Santana, Jesús, Rahoui, Farid, Stern, Daniel, Bodaghee, Arash, Alexander, David M., Barret, Didier, CNRS, Institut de Recherche en Astrophysique et Planétologie, 9 Av. colonel Roche, BP 44346, F-31028 Toulouse cedex 4, Christensen, Finn E., E-mail: f.fornasini@berkeley.edu, and and others. The NuSTAR Hard X-Ray Survey of the Norma Arm Region. United States: N. p., 2017. Web. doi:10.3847/1538-4365/AA61FC.
Fornasini, Francesca M., Tomsick, John A., Chiu, Jeng-Lun, Clavel, Maïca, Krivonos, Roman A., Boggs, Steven E., Craig, William W., Hong, JaeSub, Gotthelf, Eric V., Hailey, Charles J., Mori, Kaya, Bauer, Franz, Corral-Santana, Jesús, Rahoui, Farid, Stern, Daniel, Bodaghee, Arash, Alexander, David M., Barret, Didier, CNRS, Institut de Recherche en Astrophysique et Planétologie, 9 Av. colonel Roche, BP 44346, F-31028 Toulouse cedex 4, Christensen, Finn E., E-mail: f.fornasini@berkeley.edu, & and others. The NuSTAR Hard X-Ray Survey of the Norma Arm Region. United States. doi:10.3847/1538-4365/AA61FC.
Fornasini, Francesca M., Tomsick, John A., Chiu, Jeng-Lun, Clavel, Maïca, Krivonos, Roman A., Boggs, Steven E., Craig, William W., Hong, JaeSub, Gotthelf, Eric V., Hailey, Charles J., Mori, Kaya, Bauer, Franz, Corral-Santana, Jesús, Rahoui, Farid, Stern, Daniel, Bodaghee, Arash, Alexander, David M., Barret, Didier, CNRS, Institut de Recherche en Astrophysique et Planétologie, 9 Av. colonel Roche, BP 44346, F-31028 Toulouse cedex 4, Christensen, Finn E., E-mail: f.fornasini@berkeley.edu, and and others. Sat . "The NuSTAR Hard X-Ray Survey of the Norma Arm Region". United States. doi:10.3847/1538-4365/AA61FC.
@article{osti_22661128,
title = {The NuSTAR Hard X-Ray Survey of the Norma Arm Region},
author = {Fornasini, Francesca M. and Tomsick, John A. and Chiu, Jeng-Lun and Clavel, Maïca and Krivonos, Roman A. and Boggs, Steven E. and Craig, William W. and Hong, JaeSub and Gotthelf, Eric V. and Hailey, Charles J. and Mori, Kaya and Bauer, Franz and Corral-Santana, Jesús and Rahoui, Farid and Stern, Daniel and Bodaghee, Arash and Alexander, David M. and Barret, Didier and CNRS, Institut de Recherche en Astrophysique et Planétologie, 9 Av. colonel Roche, BP 44346, F-31028 Toulouse cedex 4 and Christensen, Finn E., E-mail: f.fornasini@berkeley.edu and and others},
abstractNote = {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{sup −14} and 4 × 10{sup −14} erg s{sup −1} cm{sup −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 log N –log S 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.},
doi = {10.3847/1538-4365/AA61FC},
journal = {Astrophysical Journal, Supplement Series},
number = 2,
volume = 229,
place = {United States},
year = {Sat Apr 01 00:00:00 EDT 2017},
month = {Sat Apr 01 00:00:00 EDT 2017}
}
  • We present a catalog of hard X-ray sources in a square-degree region surveyed by NuSTAR in the direction of the Norma spiral arm. This survey has a total exposure time of 1.7 Ms, and typical and maximum exposure depths of 50 ks and 1 Ms, respectively. In the area of deepest coverage, sensitivity limits of 5 x 10 -14 and 4 x 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 ten are detected with low significance; eight of the 38 sources are expected to be activemore » 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 multi-wavelength 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 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.« less
  • We present a catalog of 1415 X-ray sources identified in the Norma Arm Region Chandra Survey (NARCS), which covers a 2° × 0.°8 region in the direction of the Norma spiral arm to a depth of ≈20 ks. Of these sources, 1130 are point-like sources detected with ≥3σ confidence in at least one of three energy bands (0.5-10, 0.5-2, and 2-10 keV), five have extended emission, and the remainder are detected at low significance. Since most sources have too few counts to permit individual classification, they are divided into five spectral groups defined by their quantile properties. We analyze stackedmore » spectra of X-ray sources within each group, in conjunction with their fluxes, variability, and infrared counterparts, to identify the dominant populations in our survey. We find that ∼50% of our sources are foreground sources located within 1-2 kpc, which is consistent with expectations from previous surveys. Approximately 20% of sources are likely located in the proximity of the Scutum-Crux and near Norma arm, while 30% are more distant, in the proximity of the far Norma arm or beyond. We argue that a mixture of magnetic and nonmagnetic cataclysmic variables dominates the Scutum-Crux and near Norma arms, while intermediate polars and high-mass stars (isolated or in binaries) dominate the far Norma arm. We also present the cumulative number count distribution for sources in our survey that are detected in the hard energy band. A population of very hard sources in the vicinity of the far Norma arm and active galactic nuclei dominate the hard X-ray emission down to f{sub X} ≈ 10{sup –14} erg cm{sup –2} s{sup –1}, but the distribution curve flattens at fainter fluxes. We find good agreement between the observed distribution and predictions based on other surveys.« less
  • We present the first sub-arcminute images of the Galactic Center above 10 keV, obtained with NuSTAR. NuSTAR resolves the hard X-ray source IGR J17456–2901 into non-thermal X-ray filaments, molecular clouds, point sources, and a previously unknown central component of hard X-ray emission (CHXE). NuSTAR detects four non-thermal X-ray filaments, extending the detection of their power-law spectra with Γ ∼ 1.3–2.3 up to ∼50 keV. A morphological and spectral study of the filaments suggests that their origin may be heterogeneous, where previous studies suggested a common origin in young pulsar wind nebulae (PWNe). NuSTAR detects non-thermal X-ray continuum emission spatially correlated with the 6.4more » keV Fe Kα fluorescence line emission associated with two Sgr A molecular clouds: MC1 and the Bridge. Broadband X-ray spectral analysis with a Monte-Carlo based X-ray reflection model self-consistently determined their intrinsic column density (∼10{sup 23} cm{sup −2}), primary X-ray spectra (power-laws with Γ ∼ 2) and set a lower limit of the X-ray luminosity of Sgr A* flare illuminating the Sgr A clouds to L{sub X} ≳ 10{sup 38} erg s{sup −1}. Above ∼20 keV, hard X-ray emission in the central 10 pc region around Sgr A* consists of the candidate PWN G359.95–0.04 and the CHXE, possibly resulting from an unresolved population of massive CVs with white dwarf masses M{sub WD} ∼ 0.9 M{sub ⊙}. Spectral energy distribution analysis suggests that G359.95–0.04 is likely the hard X-ray counterpart of the ultra-high gamma-ray source HESS J1745–290, strongly favoring a leptonic origin of the GC TeV emission.« less
  • Results are presented for an initial survey of the Norma Arm gathered with the focusing hard X-Ray Telescope NuSTAR. The survey covers 0.2 deg{sup 2} of sky area in the 3-79 keV range with a minimum and maximum raw depth of 15 ks and 135 ks, respectively. Besides a bright black-hole X-ray binary in outburst (4U 1630–47) and a new X-ray transient (NuSTAR J163433–473841), NuSTAR locates three sources from the Chandra survey of this region whose spectra are extended above 10 keV for the first time: CXOU J163329.5–473332, CXOU J163350.9–474638, and CXOU J163355.1–473804. Imaging, timing, and spectral data from amore » broad X-ray range (0.3-79 keV) are analyzed and interpreted with the aim of classifying these objects. CXOU J163329.5–473332 is either a cataclysmic variable or a faint low-mass X-ray binary. CXOU J163350.9–474638 varies in intensity on year-long timescales, and with no multi-wavelength counterpart, it could be a distant X-ray binary or possibly a magnetar. CXOU J163355.1–473804 features a helium-like iron line at 6.7 keV and is classified as a nearby cataclysmic variable. Additional surveys are planned for the Norma Arm and Galactic Center, and those NuSTAR observations will benefit from the lessons learned during this pilot study.« less