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arXiv 1808.04775astro-ph.HE
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GRS 1739 $-$ 278在2014年爆发中的状态转变

State Transitions of GRS 1739$-$278 in the 2014 Outburst

Sili Wang, Nobuyuki Kawai, Megumi Shidatsu, Yutaro Tachibana, Taketoshi Yoshii, Masayuki Sudo, Aya Kubota

摘要:

我们基于MAXI/GSC和Swift/XRT观测报告了GRS 1739 $-$ 278在2014年爆发期间的X射线光谱分析和时间演化。在爆发的过程中,可以看到从低/硬状态到高/软状态,然后再回到低/硬状态的转变。在高/软状态期间,最内层盘温度温和地降低,而用多色盘模型估计的最内层半径保持恒定在$\sim18\ (\frac{D}{8.5\ \mathrm{kpc}}) \ {(\frac{\cos i}{\cos 30^{\circ}})}^{-1/2}$ km,其中$D$是源距离,$i$是观测倾角。吸积盘最里面的小半径表明,中心物体更可能是克尔黑洞,而不是史瓦西黑洞。将相对论盘发射模型应用于高/软态谱,基于倾斜极限$i<60^{\circ}$得到了$18.3\ \mathrm{M_{\odot}}$的质量上限,假设距离为8.5 kpc。利用跃迁光度与爱丁顿极限的经验关系,在相同的距离下,质量被约束为$4.0-18.3\ \mathrm{M_{\odot}}$。通过采用基于NuSTAR光谱与相对论模糊圆盘反射模型拟合的约束条件,可以将质量进一步约束为不大于$9.5\ \mathrm{M_{\odot}}$(Miller等人,2015)。

英文摘要:

We report on the X-ray spectral analysis and time evolution of GRS 1739$-$278 during its 2014 outburst based on MAXI/GSC and Swift/XRT observations. Over the course of the outburst, a transition from the low/hard state to the high/soft state and then back to the low/hard state was seen. During the high/soft state, the innermost disk temperature mildly decreased, while the innermost radius estimated with the multi-color disk model remained constant at $\sim18\ (\frac{D}{8.5\ \mathrm{kpc}}) \ {(\frac{\cos i}{\cos 30^{\circ}})}^{-1/2}$ km, where $D$ is the source distance and $i$ is the inclination of observation. This small innermost radius of the accretion disk suggests that the central object is more likely to be a Kerr black hole rather than a Schwardzschild black hole. Applying a relativistic disk emission model to the high/soft state spectra, a mass upper limit of $18.3\ \mathrm{M_{\odot}}$ was obtained based on the inclination limit $i<60^{\circ}$ for an assumed distance of 8.5 kpc. Using the empirical relation of the transition luminosity to the Eddington limit, the mass is constrained to $4.0-18.3\ \mathrm{M_{\odot}}$ for the same distance. The mass can be further constrained to be no larger than $9.5\ \mathrm{M_{\odot}}$ by adopting the constraints based on the fits to the NuSTAR spectra with relativistically blurred disk reflection models (Miller et al. 2015).

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