关于“NGC 6946中超亮X射线源的光谱和时间特性”，Senorita Devi等人
On `The spectral and temporal properties of an Ultra--Luminous X-ray source in NGC 6946', by Senorita Devi et al
摘要：
最近的一篇论文（arXiv：0804.3463）声称，在NGC 6946的X射线源中存在软X射线成分，这提供了强有力的证据，证明它的黑洞质量肯定是$>100\msun$，更有可能是$\sim 400\msun$，即使源是光束。我表明，数据是非常兼容的黑洞质量只有$5\msun$，辐射各向同性（即没有光束）和质量转移率约60倍的爱丁顿值，即$1.25 \times 10^{-5} \msun {\rm yr}^{-1}$。这样一个系统非常类似于银河系X射线双星天鹅座X-1的可能后代，一旦超巨星伴星进化到充满它的洛希瓣。
英文摘要：
A recent paper (arXiv:0804.3463) claims that the presence of a soft X-ray component in an X-ray source in NGC 6946 provides strong evidence that its black hole mass is definitely $>100\msun$, and more probably $\sim 400\msun$, even if the source is beamed. I show that the data are instead very compatible with a black hole mass of only $5\msun$, radiating isotropically (i.e. no beaming) and a mass transfer rate about 60 times the Eddington value, i.e. $1.25 \times 10^{-5} \msun {\rm yr}^{-1}$. Such a system is very similar to the probable descendant of the Galactic X-ray binary Cygnus X--1 once the supergiant companion evolves to fill its Roche lobe.
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