Quasiperiodic Erupters: A Stellar Mass-transfer Model for the Radiation
Quasiperiodic Erupters: A Stellar Mass-transfer Model for the Radiation
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DOI：
10.3847/1538-4357/ac9eb6
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发表时间：
2022-09
期刊：
影响因子：
--
通讯作者：
J. Krolik;Itai Linial
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文献类型：
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作者：
J. Krolik;Itai Linial
准周期喷发器是一类表现出极大振幅准周期 X 射线耀斑的非凡天体。尽管已经提出了许多动力学模型来解释它们，但相对较少的关注是利用它们的辐射特性来约束它们的动力学。在这里，我们表明，观测到的光度、光谱、重复周期、占空比和后两个量的涨落指向一个模型，在该模型中，围绕超大质量黑洞的适度偏心轨道上的主序星周期性地将质量转移到黑洞的罗希瓣；轨道动力学导致黑洞附近轻微的相对论性激波；当气体从激波流走时，会发出观察温度下的热 X 射线。耀斑本身对恒星的强烈 X 射线照射会增强质量传递，造成耀斑时间的波动，并在恒星大气中搅动湍流，从而将磁场放大到一定水平，在该水平上，磁应力可以加速传递的质量向黑洞的坠落。
Quasiperiodic erupters are a remarkable class of objects exhibiting very-large-amplitude quasiperiodic X-ray flares. Although numerous dynamical models have been proposed to explain them, relatively little attention has been given to using the properties of their radiation to constrain their dynamics. Here we show that the observed luminosity, spectrum, repetition period, duty cycle, and fluctuations in the latter two quantities point toward a model in which a main-sequence star on a moderately eccentric orbit around a supermassive black hole periodically transfers mass to the Roche lobe of the black hole; orbital dynamics lead to mildly relativistic shocks near the black hole; and thermal X-rays at the observed temperature are emitted by the gas as it flows away from the shock. Strong X-ray irradiation of the star by the flare itself augments the mass transfer, creates fluctuations in flare timing, and stirs turbulence in the stellar atmosphere that amplifies the magnetic field to a level at which magnetic stresses can accelerate infall of the transferred mass toward the black hole.