Low-mass X-ray binaries in the bulge of the Milky Way
Low-mass X-ray binaries in the bulge of the Milky Way
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DOI：
10.1051/0004-6361:200810115
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发表时间：
2008-05
影响因子：
6.5
通讯作者：
M.Revnivtsev;A.Lutovinov;E.Churazov;S.Sazonov;M.Gilfanov;S.Grebenev;R. Mpa;Garching;Germany;-. Iki;Moscow;Russia.
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文献类型：
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作者：
M.Revnivtsev;A.Lutovinov;E.Churazov;S.Sazonov;M.Gilfanov;S.Grebenev;R. Mpa;Garching;Germany;-. Iki;Moscow;Russia.
我们研究人口的低质量X射线双星（LMXBs）在银河系隆起使用深调查这一地区的IBIS望远镜搭载的INTEGRAL天文台。由于相对于该领域以前的调查增加了灵敏度，我们成功地探测了LMXB的光度函数（LF），在17−60 keV的能带中下降到107 × 10 34 erg/s。17−60 keV LF在10 35 −10 37 erg/s范围内的斜率为d log N/ dl ogL = −0.96 ± 0.20。在这些低光度下，LMXB在2 - 60 keV之间的光谱与蟹状星云的光谱相似，因此在标准（2 - 10 keV）和硬（17 - 60 keV）X射线波段释放出几乎相等的能量。这意味着LMXB LF在10 35 - 10 37 erg/s的光度范围内，在17 - 60 keV和2 - 10 keV的能带都是平坦的。这进一步表明，2−10 keV LF的暗端明显比其亮端（高于10 37 erg/s）平坦，之前测量的斜率为d logN/ dl ogL <$− 1.8。我们讨论这种扁平化的起源。我们还表明，持久的LMXB在银河系中心/银河系凸起区域的空间分布是一致的恒星质量分布的模型，包括核恒星盘组件在银河系的最内层的程度。在银河系中心区域检测到的瞬态LMXB的空间分布表明，相对于外部区域，在银河系最内层的瞬态源的比例增加。
We study the population of low-mass X-ray binaries (LMXBs) in the Galactic bulge using the deep survey of this region by the IBIS telescope aboard the INTEGRAL observatory. Thanks to the increased sensitivity with respect to previous surveys of this field, we succeeded in probing the luminosity function (LF) of LMXBs down to ∼7 × 10 34 erg/s in the 17−60 keV energy band. The slope of the 17−60 keV LF in the 10 35 −10 37 erg/s range is d log N/ dl ogL = −0.96 ± 0.20. At these low luminosities, the spectra of LMXBs between 2 and 60 keV are similar to that of the Crab, and therefore nearly equal amounts of energy are released in the standard (2−10 keV) and hard (17−60 keV) X-ray bands. This implies that the LMXB LF is flat both in the 17−60 keV and 2−10 keV energy bands over the 10 35 −10 37 erg/s luminosity range. This further suggests that the faint end of the 2−10 keV LF is significantly flatter than its bright end (above 10 37 erg/s), where a slope of d logN/ dl ogL ∼− 1.8 was previously measured. We discuss the origin of this flattening. We also demonstrate that the spatial distribution of persistent LMXBs in the Galactic center/Galactic bulge region is consistent with a model of stellar mass distribution that includes the nuclear stellar disk component in the innermost degree of the Galaxy. The spatial distribution of transient LMXBs detected in the Galactic center region indicates an increased fraction of transient sources in the innermost degree of the Galaxy with respect to outer regions.