SPECTRAL PROPERTIES OF X-RAY BINARIES IN CENTAURUS A
SPECTRAL PROPERTIES OF X-RAY BINARIES IN CENTAURUS A
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DOI：
10.1088/0004-637x/766/2/88
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发表时间：
2013-02
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通讯作者：
M. Burke;Somak Raychaudhury;R. Kraft;T. Maccarone;N. Brassington;M. Hardcastle;J. Kainulainen;K. Woodley;J. Goodger;G. Sivakoff;W. Forman;C. Jones;S. Murray;M. Birkinshaw;J. Croston;D. Evans;M. Gilfanov;A. Jordán;C. Sarazin;R. Voss;D. Worrall;Zhongli Zhang
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作者：
M. Burke;Somak Raychaudhury;R. Kraft;T. Maccarone;N. Brassington;M. Hardcastle;J. Kainulainen;K. Woodley;J. Goodger;G. Sivakoff;W. Forman;C. Jones;S. Murray;M. Birkinshaw;J. Croston;D. Evans;M. Gilfanov;A. Jordán;C. Sarazin;R. Voss;D. Worrall;Zhongli Zhang
我们提出了一个光谱调查的X射线双星（XBs）在NGC 5128（Cen A），使用六个100千分之一钱德拉观测在2007年的两个多月。根据拟合吸收柱NH的行为，我们将样品分为热主导态和非热主导态，并给出了Lx = 2 × 1037 erg s−1的源的光谱参数。大多数的来源是一致的中子星星低质量X射线双星（NS LMXB），我们确定了三个瞬态黑洞（BH）LMXB候选人符合尘埃带，这是一个小的晚型星系的残余。我们的研究结果也提供了初步的支持，明显的“差距”的质量分布之间的紧凑的对象202 -5 M的。我们建议，BH LMXB优先发现在尘埃带，并建议这是因为年轻的恒星人口。在Cen A晕中，大多数（约70%-80%）潜在的罗氏叶填充施主都是120亿年，而BH LMXB需要施主120亿年才能产生观测到的峰值亮度。这种对更大质量施主的要求也可以解释最近的结果，即对于早期类型星系的XB星族，X射线光度函数随着年龄在Lx = 1038 erg s−1而变陡;对于更老的恒星星族，形成更明亮的光源所需的恒星数量更少。
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 NH, and present the spectral parameters of sources with Lx ≳ 2 × 1037 erg s−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 ∼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 Lx ⩾ 5 × 1038 erg s−1 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.