SPECTRAL PROPERTIES OF X-RAY BINARIES IN CENTAURUS A

Journal Article · Mon Apr 01 00:00:00 EDT 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/766/2/88· OSTI ID:22167511

Burke, Mark J.; Raychaudhury, Somak ^[1]; Kraft, Ralph P.; Forman, William R.; Jones, Christine; Murray, Stephen S.; Birkinshaw, Mark; Evans, Daniel A.; Jordan, Andres ^[2]; Maccarone, Thomas J.; Croston, Judith H. ^[3]; Brassington, Nicola J.; Hardcastle, Martin J.; Goodger, Joanna L. ^[4]; Kainulainen, Jouni ^[5]; Woodley, Kristin A. ^[6]; Sivakoff, Gregory R. ^[7]; Gilfanov, Marat ^[8]; Sarazin, Craig L. ^[9]; Voss, Rasmus ^[10] ; others, and

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1. School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)
2. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
3. School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom)
4. School of Physics, Astronomy, and Mathematics, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom)
5. Max-Planck-Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany)
6. Department of Physics and Astronomy, University of British Columbia, Vancouver BC V6T 1Z1 (Canada)
7. Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1 (Canada)
8. Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, D-85741, Garching (Germany)
9. Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States)
10. Department of Astrophysics/IMAPP, Radboud, University Nijmegen, P.O. Box 9010, NL-6500 GL Nijmegen (Netherlands)

We present a spectral investigation of X-ray binaries (XBs) in NGC 5128 (Cen A), using six 100 ks Chandra observations taken over two months in 2007. We divide our sample into thermally and non-thermally dominated states based on the behavior of the fitted absorption column N{sub H}, and present the spectral parameters of sources with L{sub x} {approx}> 2 Multiplication-Sign 10{sup 37} erg s{sup -1}. The majority of sources are consistent with being neutron star low-mass X-ray binaries (NS LMXBs) and we identify three transient black hole (BH) LMXB candidates coincident with the dust lane, which is the remnant of a small late-type galaxy. Our results also provide tentative support for the apparent 'gap' in the mass distribution of compact objects between {approx}2-5 M{sub Sun }. We propose that BH LMXBs are preferentially found in the dust lane, and suggest this is because of the younger stellar population. The majority ({approx}70%-80%) of potential Roche lobe filling donors in the Cen A halo are {approx}> 12 Gyr old, while BH LMXBs require donors {approx}> 1 M{sub Sun} to produce the observed peak luminosities. This requirement for more massive donors may also explain recent results that claim a steepening of the X-ray luminosity function with age at L{sub x} {>=} 5 Multiplication-Sign 10{sup 38} erg s{sup -1} for the XB population of early-type galaxies; for older stellar populations, there are fewer stars {approx}> 1 M{sub Sun }, which are required to form the more luminous sources.

• OSTI ID: 22167511
• Journal Information: Astrophysical Journal, Vol. 766, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABSORPTION
BINARY STARS
BLACK HOLES
COSMIC DUST
LUMINOSITY
MASS DISTRIBUTION
NEUTRON STARS
ROCHE EQUIPOTENTIALS
X-RAY GALAXIES