| dc.identifier.citation | Burke , M J , Raychaudhury , S , Kraft , R P , Forman , W R , Jones , C , Murray , S S , Birkinshaw , M , Evans , D A , Jordán , A , Worrall , D M , Maccarone , T J , Croston , J H , Brassington , N , Hardcastle , M J , Goodger , J L , Kainulainen , J , Woodley , K A , Sivakoff , G R , Gilfanov , M , Zhang , Z , Sarazin , C L & Voss , R 2013 , ' Spectral properties of X-ray binaries in Centaurus A ' , The Astrophysical Journal , vol. 766 , no. 2 , 88 . https://doi.org/10.1088/0004-637X/766/2/88 | |
| dc.description.abstract | 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 , and present the spectral parameters of sources with L ≳ 2 × 10 erg s. 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 ∼2-5 M . We propose that BH LMXBs are preferentially found in the dust lane, and suggest this is because of the younger stellar population. The majority (∼70%-80%) of potential Roche lobe filling donors in the Cen A halo are ≳ 12 Gyr old, while BH LMXBs require donors ≳ 1 M 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 ≥ 5 × 10 erg s for the XB population of early-type galaxies; for older stellar populations, there are fewer stars ≳ 1 M , which are required to form the more luminous sources. | en |
