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arXiv 0810.4458astro-ph
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同步辐射锅炉与黑洞双星的光谱态

The synchrotron boiler and the spectral states of black hole binaries

Julien Malzac, Renaud Belmont

摘要:

本文研究了同步辐射自吸收对吸积黑洞磁化日冕中康普顿化电子分布的影响。我们解决的动力学方程,假设电源是通过库仑碰撞与人口的热质子和/或通过注入的非热高能电子的一些未指定的加速过程中提供给日冕电子。我们数值计算了稳态粒子分布和逃逸光子谱。这些数值模拟证实,同步辐射自吸收,以及电子-电子库仑碰撞,构成了一个有效的热化机制的日冕电子。当比较的数据,他们允许我们约束的磁场和温度的热质子在日冕中独立于任何动态吸积流模型或几何形状。与天鹅座X-1的低硬态(LHS)光谱的初步比较表明,磁场低于辐射均分,这表明日冕不是通过磁场耗散(如大多数吸积盘日冕模型所假设的那样)提供动力的。然而,在天鹅座X-1和其他来源的LHS中,我们的结果也指向质子温度大大低于ADAF模型预测的温度。相比之下,在高软态(HSS)中,质子温度和磁场都可以高得多。我们还表明,在这两种光谱状态的磁化电晕可以供电基本上通过非热粒子的加速。LHS和HSS日冕发射之间的主要差异可以理解为HSS中更强的辐射冷却的结果,由来自几何上薄的吸积盘的软热辐射引起。

英文摘要:

We study the effects of synchrotron self-absorption on the Comptonising electron distribution in the magnetised corona of accreting black holes. We solve the kinetic equations assuming that power is supplied to the coronal electrons through Coulomb collisions with a population of hot protons and/or through the injection of non-thermal energetic electrons by some unspecified acceleration process. We compute numerically the steady state particle distributions and escaping photon spectra. These numerical simulations confirm that synchrotron self-absorption, together with e-e Coulomb collisions, constitute an efficient thermalising mechanism for the coronal electrons. When compared to the data, they allow us to constrain the magnetic field and temperature of the hot protons in the corona independently of any dynamical accretion flow model or geometry. A preliminary comparison with the Low Hard State (LHS) spectrum of Cygnus X-1 indicates a magnetic field below equipartition with radiation, suggesting that the corona is not powered through magnetic field dissipation (as assumed in most accretion disc corona models). However, in the LHS of Cygnus X-1 and other sources, our results also point toward proton temperatures substantially lower than what predicted by the ADAF-like models. In contrast, in the High Soft State (HSS) both the proton temperature and magnetic field could be much higher. We also show that in both spectral states the magnetised corona could be powered essentially through acceleration of non-thermal particles. The main differences between the LHS and HSS coronal emission can then be understood as the consequence of the much stronger radiative cooling in the HSS caused by the soft thermal radiation coming from the geometrically thin accretion disc.

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