A mass of less than 15 solar masses for the black hole in an ultraluminous X-ray source
A mass of less than 15 solar masses for the black hole in an ultraluminous X-ray source
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DOI：
10.1038/nature13730
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发表时间：
2014-10
期刊：
影响因子：
64.8
通讯作者：
C. Motch;M. Pakull;R. Soria;F. Grisé;G. Pietrzyński;G. Pietrzyński
中科院分区：
文献类型：
--
作者：
C. Motch;M. Pakull;R. Soria;F. Grisé;G. Pietrzyński;G. Pietrzyński
大多数超亮X射线源具有一组在银河系恒星质量黑洞中看不到的典型性质。它们的光度超过每秒3 × 1039尔格，具有异常的软X射线成分（典型的温度低于0.3千电子伏特），并且在其光谱中有一个特征性的下降，超过约5千电子伏特。这种令人困惑的性质被解释为中等质量黑洞的证据，或者是恒星质量黑洞的辐射，其吸积超过爱丁顿极限，类似于一些处于峰值亮度的银河系黑洞。最近，在一个罕见的瞬时恒星质量黑洞中观察到了非常软的X射线谱。本文报道星系NGC 7793中的X射线源P13是一个周期约为64天的双星系统，具有超亮源的三种典型性质。通过模拟B9 Ia施主星星的X射线加热所产生的强光学和紫外调制，我们将黑洞质量限制在15个太阳质量以下。我们的结果表明，在P13，软热辐射和光谱曲率确实是超临界吸积的签名。以此类推，具有相似X射线光谱和高达每秒1040尔格几倍的光度的超亮X射线源可以用超临界吸积到大质量恒星质量黑洞上来解释。
Most ultraluminous X-ray sources have a typical set of properties not seen in Galactic stellar-mass black holes. They have luminosities of more than 3 × 1039ergs per second, unusually soft X-ray components (with a typical temperature of less than about 0.3 kiloelectronvolts) and a characteristic downturn,in their spectra above about 5 kiloelectronvolts. Such puzzling properties have been interpreted either as evidence of intermediate-mass black holes,or as emission from stellar-mass black holes accreting above their Eddington limit,, analogous to some Galactic black holes at peak luminosity,. Recently, a very soft X-ray spectrum was observed in a rare and transient stellar-mass black hole. Here we report that the X-ray source P13 in the galaxy NGC 7793 is in a binary system with a period of about 64 days and exhibits all three canonical properties of ultraluminous sources. By modelling the strong optical and ultraviolet modulations arising from X-ray heating of the B9Ia donor star, we constrain the black hole mass to be less than 15 solar masses. Our results demonstrate that in P13, soft thermal emission and spectral curvature are indeed signatures of supercritical accretion. By analogy, ultraluminous X-ray sources with similar X-ray spectra and luminosities of up to a few times 1040ergs per second can be explained by supercritical accretion onto massive stellar-mass black holes.