论文标题
SGR A*和M87*中热积聚流中直接电子加热的观察性约束
Observational Constraints on Direct Electron Heating in the Hot Accretion Flows in Sgr A* and M87*
论文作者
论文摘要
热积聚理论中的一个重要参数围绕黑洞，$δ$是$Δ$，它描述了直接进入加热电子的吸积流中``粘性''耗散能量的比例。对于给定的质量积聚率，热积聚流的辐射效率由$δ$确定。不幸的是，从第一原则中很难确定$δ$的值。最近的事件范围望远镜协作（EHTC）在M87*和sgr a*上结果提供了不同的约束$δ$的方式。通过将EHTC估计的M87*和SGR A*中的质量积聚率与两个来源的测量辐射光度估计，我们对相应积聚流的辐射效率产生了良好的约束。同时，我们使用的是热磁性磁盘（MAD）的理论模型来计算预期的辐射效率作为$δ$（和增生率）的函数。通过将EHTC衍生的辐射效率与MAD模型的理论结果进行比较，我们发现SGR A*需要$δ\ ga 0.3 $。 ％最有可能的值为$δ\ sim 0.5 $。在M87*的情况下，类似的比较给出了不确定的结果，因为该来源的积聚率仍然存在很大的不确定性。
An important parameter in the theory of hot accretion flows around black holes is $δ$, which describes the fraction of ``viscously'' dissipated energy in the accretion flow that goes directly into heating electrons. For a given mass accretion rate, the radiative efficiency of a hot accretion flow is determined by $δ$. Unfortunately, the value of $δ$ is hard to determine from first principles. The recent Event Horizon Telescope Collaboration (EHTC) results on M87* and Sgr A* provide us with a different way of constraining $δ$. By combining the mass accretion rates in M87* and Sgr A* estimated by the EHTC with the measured bolometric luminosities of the two sources, we derive good constraints on the radiative efficiencies of the respective accretion flows. In parallel, we use a theoretical model of hot magnetically arrested disks (MAD) to calculate the expected radiative efficiency as a function of $δ$ (and accretion rate). By comparing the EHTC-derived radiative efficiencies with the theoretical results from MAD models, we find that Sgr A* requires $δ\ga 0.3$. %with the most likely value being $δ\sim 0.5$. A similar comparison in the case of M87* gives inconclusive results as there is still a large uncertainty in the accretion rate in this source.
