Sgr A* 的低angular momentum流量模型II
Low angular momentum flow model II for Sgr A*
摘要：
采用最近对Sgr A* 附近恒星的星风分析中估计的比角动量λ、总比能量ε和输入吸积率\dot M_{input} = 4.0 × 10 ^{-6}太阳质量/年，研究了超大质量黑洞周围的一维双温吸积流.即使考虑离子对电子的加热、韧致辐射冷却和同步辐射冷却，只要磁能密度与热能密度之比β< 1，双温流几乎是绝热的。离子和电子的不同温度是由离子和电子的不同绝热指数引起的，绝热指数取决于它们在相对论区域下的温度状态。总光度随β的增加而增加，当β=10 ^{-3}-1时，总光度为-10 ^{35}-10 ^{36} erg/s。此外，从上述流动的二维含时流体动力学计算中，我们发现，不规则振荡激波形成在内部区域，光度和质量流出率的变化分别为2 - 3和1.5 - 4倍。时间变化可能与Sgr A* 的耀斑活动有关。
英文摘要：
We examine 1D two-temperature accretion flows around a supermassive black hole, adopting the specific angular momentum λ, the total specific energy εand the input accretion rate \dot M_{input} = 4.0x10^{-6} solar mass/yr estimated in the recent analysis of stellar wind of nearby stars around Sgr A*. The two-temperature flow is almost adiabatic even if we take account of the heating of electrons by ions, the bremsstrahlung cooling and the synchrotron cooling, as long as the ratio βof the magnetic energy density to the thermal energy density is taken to be as β< 1. The different temperatures of ions and electrons are caused by the different adiabatic indices of ions and electrons which depend on their temperature states under the relativistic regime. The total luminosity increases with increasing βand results in - 10^{35} - 10^{36} erg/s for β=10^{-3} - 1. Furthermore, from 2D time-dependent hydrodynamical calculations of the above flow, we find that the irregularly oscillating shocks are formed in the inner region and that the luminosity and the mass-outflow rate vary by a factor of 2 -- 3 and 1.5 -- 4, respectively. The time variability may be relevant to the flare activity of Sgr A*.
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