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Title: Galactic Sources Detected in the NuSTAR Serendipitous Survey

Abstract

The Nuclear Spectroscopic Telescope Array (NuSTAR) provides an improvement in sensitivity at energies above 10 keV by two orders of magnitude over non-focusing satellites, making it possible to probe deeper into the Galaxy and universe. Lansbury and collaborators recently completed a catalog of 497 sources serendipitously detected in the 3–24 keV band using 13 deg{sup 2} of NuSTAR coverage. Here, we report on an optical and X-ray study of 16 Galactic sources in the catalog. We identify 8 of them as stars (but some or all could have binary companions), and use information from Gaia to report distances and X-ray luminosities for 3 of them. There are 4 CVs or CV candidates, and we argue that NuSTAR J233426–2343.9 is a relatively strong CV candidate based partly on an X-ray spectrum from XMM-Newton . NuSTAR J092418–3142.2, which is the brightest serendipitous source in the Lansbury catalog, and NuSTAR J073959–3147.8 are low-mass X-ray binary candidates, but it is also possible that these 2 sources are CVs. One of the sources is a known high-mass X-ray binary (HMXB), and NuSTAR J105008–5958.8 is a new HMXB candidate that has strong Balmer emission lines in its optical spectrum and a hard X-ray spectrum. We discuss the implications of finding these HMXBs for the surfacemore » density (log N –log S ) and luminosity function of Galactic HMXBs. We conclude that with the large fraction of unclassified sources in the Galactic plane detected by NuSTAR in the 8–24 keV band, there could be a significant population of low-luminosity HMXBs.« less

Authors:
; ;  [1]; ;  [2];  [3]; ; ;  [4];  [5];  [6]; ;  [7];  [8];  [9];  [10]
  1. Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450 (United States)
  2. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)
  3. Department of Astronomy, Harvard University, 60 Garden Street, Cambridge, MA 02138 (United States)
  4. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
  5. Centre for Extragalactic Astronomy, Department of Physics, University of Durham, South Road, Durham DH1 3LE (United Kingdom)
  6. Georgia College and State University, Milledgeville, GA 31061 (United States)
  7. Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States)
  8. California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States)
  9. Space Research Institute of the Russian Academy of Sciences, Profsoyuznaya Str. 84/32, 117997, Moscow (Russian Federation)
  10. Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)
Publication Date:
OSTI Identifier:
22661114
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal, Supplement Series; Journal Volume: 230; 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; DENSITY; HARD X RADIATION; KEV RANGE; LUMINOSITY; MASS; MILKY WAY; PROBES; SATELLITES; SENSITIVITY; SURFACES; TELESCOPES; UNIVERSE; WHITE DWARF STARS; X-RAY SPECTRA

Citation Formats

Tomsick, John A., Clavel, Maïca, Chiu, Jeng-Lun, Lansbury, George B., Aird, James, Rahoui, Farid, Fornasini, Francesca M., Hong, JaeSub, Grindlay, Jonathan E., Alexander, David M., Bodaghee, Arash, Hailey, Charles J., Mori, Kaya, Harrison, Fiona A., Krivonos, Roman A., and Stern, Daniel. Galactic Sources Detected in the NuSTAR Serendipitous Survey. United States: N. p., 2017. Web. doi:10.3847/1538-4365/AA7517.
Tomsick, John A., Clavel, Maïca, Chiu, Jeng-Lun, Lansbury, George B., Aird, James, Rahoui, Farid, Fornasini, Francesca M., Hong, JaeSub, Grindlay, Jonathan E., Alexander, David M., Bodaghee, Arash, Hailey, Charles J., Mori, Kaya, Harrison, Fiona A., Krivonos, Roman A., & Stern, Daniel. Galactic Sources Detected in the NuSTAR Serendipitous Survey. United States. doi:10.3847/1538-4365/AA7517.
Tomsick, John A., Clavel, Maïca, Chiu, Jeng-Lun, Lansbury, George B., Aird, James, Rahoui, Farid, Fornasini, Francesca M., Hong, JaeSub, Grindlay, Jonathan E., Alexander, David M., Bodaghee, Arash, Hailey, Charles J., Mori, Kaya, Harrison, Fiona A., Krivonos, Roman A., and Stern, Daniel. Thu . "Galactic Sources Detected in the NuSTAR Serendipitous Survey". United States. doi:10.3847/1538-4365/AA7517.
@article{osti_22661114,
title = {Galactic Sources Detected in the NuSTAR Serendipitous Survey},
author = {Tomsick, John A. and Clavel, Maïca and Chiu, Jeng-Lun and Lansbury, George B. and Aird, James and Rahoui, Farid and Fornasini, Francesca M. and Hong, JaeSub and Grindlay, Jonathan E. and Alexander, David M. and Bodaghee, Arash and Hailey, Charles J. and Mori, Kaya and Harrison, Fiona A. and Krivonos, Roman A. and Stern, Daniel},
abstractNote = {The Nuclear Spectroscopic Telescope Array (NuSTAR) provides an improvement in sensitivity at energies above 10 keV by two orders of magnitude over non-focusing satellites, making it possible to probe deeper into the Galaxy and universe. Lansbury and collaborators recently completed a catalog of 497 sources serendipitously detected in the 3–24 keV band using 13 deg{sup 2} of NuSTAR coverage. Here, we report on an optical and X-ray study of 16 Galactic sources in the catalog. We identify 8 of them as stars (but some or all could have binary companions), and use information from Gaia to report distances and X-ray luminosities for 3 of them. There are 4 CVs or CV candidates, and we argue that NuSTAR J233426–2343.9 is a relatively strong CV candidate based partly on an X-ray spectrum from XMM-Newton . NuSTAR J092418–3142.2, which is the brightest serendipitous source in the Lansbury catalog, and NuSTAR J073959–3147.8 are low-mass X-ray binary candidates, but it is also possible that these 2 sources are CVs. One of the sources is a known high-mass X-ray binary (HMXB), and NuSTAR J105008–5958.8 is a new HMXB candidate that has strong Balmer emission lines in its optical spectrum and a hard X-ray spectrum. We discuss the implications of finding these HMXBs for the surface density (log N –log S ) and luminosity function of Galactic HMXBs. We conclude that with the large fraction of unclassified sources in the Galactic plane detected by NuSTAR in the 8–24 keV band, there could be a significant population of low-luminosity HMXBs.},
doi = {10.3847/1538-4365/AA7517},
journal = {Astrophysical Journal, Supplement Series},
number = 2,
volume = 230,
place = {United States},
year = {Thu Jun 01 00:00:00 EDT 2017},
month = {Thu Jun 01 00:00:00 EDT 2017}
}
  • 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
  • We present a study of the X-ray properties of five Galactic supernova remnants (SNRs)—Kes 17 (G304.6+0.1), G311.5–0.3, G346.6–0.2, CTB 37A (G348.5+0.1), and G348.5–0.0—that were detected in the infrared by Reach et al. in an analysis of data from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) that was conducted by the Spitzer Space Telescope. We present and analyze archival ASCA observations of Kes 17, G311.5–0.3, and G346.6–0.2, archival XMM-Newton observations of Kes 17, CTB 37A, and G348.5–0.0, and an archival Chandra observation of CTB 37A. All of the SNRs are clearly detected in the X-ray except possibly G348.5–0.0. Our studymore » reveals that the four detected SNRs all feature center-filled X-ray morphologies and that the observed emission from these sources is thermal in all cases. We argue that these SNRs should be classified as mixed-morphology SNRs (MM SNRs); our study strengthens the correlation between MM SNRs and SNRs interacting with molecular clouds and suggests that the origin of MM SNRs may be due to the interactions between these SNRs and adjacent clouds. Our ASCA analysis of G311.5–0.3 reveals for the first time X-ray emission from this SNR: the X-ray emission is center-filled within the radio and infrared shells and thermal in nature (kT ∼ 0.98 keV), thus motivating its classification as an MM SNR. We find considerable spectral variations in the properties associated with the plasmas of the other X-ray-detected SNRs, such as a possible overabundance of magnesium in the plasma of Kes 17. Our new results also include the first detailed spatially resolved spectroscopic study of CTB 37A using Chandra as well as a spectroscopic study of the discrete X-ray source CXOU J171428.5–383601, which may be a neutron star associated with CTB 37A. Finally, we also estimate such properties as electron density n{sub e} , radiative age t {sub rad} and swept-up mass M{sub X} for each of the four X-ray-detected SNRs. Each of these values are comparable to archetypal MM SNRs like 3C 391 and W44. In an analysis of the spectrum of Kes 17, we did not find evidence of overionization unlike other archetypal MM SNRs like W44 and W49B.« less
  • The discovery of a new ab-type RR Lyrae variable, projected in front of the giant elliptical galaxy NGC 4472 in the Virgo Cluster, is reported. CCD photometry of the star shows it has a period of 0.6661 day, a mean V magnitude of 19.23, and a V amplitude of 0.40 mg. These properties place the star far above the Galactic plane and about 50 kpc from the Galactic center, making it the field halo star with the largest well-established distance now known. 23 refs.
  • We present the results of X-ray spectral analysis of 22 active galactic nuclei (AGNs) with a small scattering fraction selected from the Second XMM-Newton Serendipitous Source Catalogue using hardness ratios. They are candidates of buried AGNs, since a scattering fraction, which is a fraction of scattered emission by the circumnuclear photoionized gas with respect to direct emission, can be used to estimate the size of the opening part of an obscuring torus. Their X-ray spectra are modeled by a combination of a power law with a photon index of 1.5-2 absorbed by a column density of approx10{sup 23-24} cm{sup -2},more » an unabsorbed power law, narrow Gaussian lines, and some additional soft components. We find that scattering fractions of 20 among 22 objects are less than a typical value (approx3%) for Seyfert 2s observed so far. In particular, those of eight objects are smaller than 0.5%, which are in the range for buried AGNs found in recent hard X-ray surveys. Moreover, [O III] lambda5007 luminosities at given X-ray luminosities for some objects are smaller than those for Seyfert 2s previously known. This fact could be interpreted as a smaller size of optical narrow emission-line regions produced in the opening direction of the obscuring torus. These results indicate that they are strong candidates for the AGN buried in a very geometrically thick torus.« less
  • We report on the serendipitous discovery in the Blanco Cosmology Survey (BCS) imaging data of a z = 0.9057 galaxy that is being strongly lensed by a massive galaxy cluster at a redshift of z = 0.3838. The lens (BCS J2352-5452) was discovered while examining i- and z-band images being acquired in 2006 October during a BCS observing run. Follow-up spectroscopic observations with the Gemini Multi-Object Spectrograph instrument on the Gemini-South 8 m telescope confirmed the lensing nature of this system. Using weak-plus-strong lensing, velocity dispersion, cluster richness N{sub 200}, and fitting to a Navarro-Frenk-White (NFW) cluster mass density profile,more » we have made three independent estimates of the mass M{sub 200} which are all very consistent with each other. The combination of the results from the three methods gives M{sub 200} = (5.1 {+-} 1.3) Multiplication-Sign 10{sup 14} M{sub Sun }, which is fully consistent with the individual measurements. The final NFW concentration c{sub 200} from the combined fit is c{sub 200} = 5.4{sup +1.4}{sub -1.1}. We have compared our measurements of M{sub 200} and c{sub 200} with predictions for (1) clusters from {Lambda}CDM simulations, (2) lensing-selected clusters from simulations, and (3) a real sample of cluster lenses. We find that we are most compatible with the predictions for {Lambda}CDM simulations for lensing clusters, and we see no evidence based on this one system for an increased concentration compared to {Lambda}CDM. Finally, using the flux measured from the [O II]3727 line we have determined the star formation rate of the source galaxy and find it to be rather modest given the assumed lens magnification.« less