Synchrotron Self-Compton Scattering in Sgr A* Derived from NIR and X-Ray Flare Statistics
Synchrotron Self-Compton Scattering in Sgr A* Derived from NIR and X-Ray Flare Statistics
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DOI：
10.3847/1538-4357/ab9947
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发表时间：
2020-07
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影响因子：
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通讯作者：
M. Subroweit;E. Mossoux;A. Eckart
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作者：
M. Subroweit;E. Mossoux;A. Eckart
射手座A*(SgrA*)的耀斑活动可以用统计方法进行分析，以检验其吸积流的发射模型。一个特殊的建模问题是，观测到的X射线耀斑是同步加速器光谱的高能端，还是来自较低能量同步加速器过程的自康普顿光子。我们使用已经发表的钱德拉X射线远景计划数据来统计研究SgrA*的X射线计数率分布。之前的两个工作组已经对该数据进行了这样的分析。他们用有界的幂定律来模拟发射的耀斑部分，即在最高测量计数率下具有硬截止的幂定律分布。在这个模型下，两个团队都得到了一个幂定律指数。我们发现耀斑的计数率分布也可以用截断的，即指数衰减的幂定律来描述。我们认为，指数截断比硬截断更自然。对于这个替代模型，我们的拟合度得到了一个幂定律指数。我们发现，这个斜率可以用同步加速器自康普顿(SSC)过程来解释。因此，我们认为SSC模型是最适合解释观测到的X射线计数率分布的模型。
The flaring activity of Sagittarius A* (Sgr A*) can be analyzed by statistical means to test emission models for its accretion flow. A particular modeling question is whether the observed X-ray flares are the high-energy end of a synchrotron spectrum or if they arise from self-Comptonized photons of a lower-energy synchrotron process. We use already published Chandra X-ray Visionary Project data to statistically investigate the X-ray count-rate distribution of Sgr A*. Two previous workgroups have already undertaken such an analysis on that data. They modeled the flaring part of the emission with a bounded power law, i.e., a power-law distribution with a hard cutoff at the highest measured count rate. With this model, both teams obtain a power-law index . We show that the flare count-rate distribution can also be well described by a truncated, i.e., an exponentially decaying power law. We argue that an exponential truncation is a more natural model than a hard cutoff. With this alternate model, our fit yields a power-law index . We find that this slope can be canonically explained by a synchrotron self-Compton (SSC) process. Therefore, we argue that SSC models are the best ones suitable to explain the observed X-ray count-rate distribution.