人马座A盘不稳定性的广义相对论通量调制
General Relativistic Flux Modulations from Disk Instabilities in Sagittarius A*
摘要：
我们在银河系中心的超大质量黑洞Sgr A* 中探测到了近红外和X射线耀斑，其（准）周期约为17-20分钟，表明在事件视界上方只有几个史瓦西半径的发射区。最新的X射线耀斑，用XMM-牛顿探测到，是值得注意的，其详细的光曲线，产生不仅是迄今为止最高质量的周期，但也反映了发射区域的几何结构的重要结构。最近对Sgr A* 盘的MHD模拟已经证明了Rossby波不稳定性的增长，这增强了几个小时的吸积速率，可能是观测到的耀斑的原因。在这封信中，我们在史瓦西度规中进行射线追踪计算，以尽可能准确地确定在这种破坏过程中由广义相对论效应产生的光变曲线。我们发现，Rossby波诱导的螺旋图案的磁盘是一个很好的拟合的数据，这意味着磁盘倾角约77度。然而，请注意，如果这种关联是正确的，观察到的周期不是由于基础的开普勒运动，而是由于模式速度。观测到的光变曲线和模拟的光变曲线之间的有利比较提供了重要的额外证据，表明耀斑是在Sgr A* 的内盘中产生的。
英文摘要：
Near-IR and X-ray flares have been detected from the supermassive black hole Sgr A* at the center of our Galaxy with a (quasi)-period of ~17-20 minutes, suggesting an emission region only a few Schwarzschild radii above the event horizon. The latest X-ray flare, detected with XMM-Newton, is notable for its detailed lightcurve, yielding not only the highest quality period thus far, but also important structure reflecting the geometry of the emitting region. Recent MHD simulations of Sgr A*'s disk have demonstrated the growth of a Rossby wave instability, that enhances the accretion rate for several hours, possibly accounting for the observed flares. In this Letter, we carry out ray-tracing calculations in a Schwarzschild metric to determine as accurately as possible the lightcurve produced by general relativistic effects during such a disruption. We find that the Rossby wave induced spiral pattern in the disk is an excellent fit to the data, implying a disk inclination angle of ~77 deg. Note, however, that if this association is correct, the observed period is not due to the underlying Keplerian motion but, rather, to the pattern speed. The favorable comparison between the observed and simulated lightcurves provides important additional evidence that the flares are produced in Sgr A*'s inner disk.
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