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arXiv 0810.4589astro-ph
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微类星体的X射线谱态

X-ray spectral states of microquasars

Julien Malzac, Renaud Belmont

摘要:

我们讨论的起源观察到的显着不同的X射线光谱形状的低硬状态(LHS:为主的热comptonisation)和高软状态(HSS:为主的吸积盘热发射和非热comptonisation在日冕)。我们使用一种新的代码来进行数值模拟,该代码考虑了所谓的同步加速器锅炉效应。这些数值模拟的数据相比,使我们能够约束的磁场和温度的热质子在日冕。对于天鹅座X-1的硬态,我们发现一个低于辐射均分的磁场,这表明日冕不是通过磁场耗散供电的(如大多数吸积盘日冕模型所假设的那样)。另一方面,我们的研究结果也指向质子温度,大大低于ADAF模型的典型温度。最后,我们表明,在这两种光谱状态Comptonising等离子体可以供电基本上通过幂律加速的非热电子,然后部分热化的同步加速器和库仑锅炉。这表明,与目前的看法相反,HSS和LHS的日冕可能具有非常相似的性质。LHS和HSS日冕光谱之间的差异主要是由HSS中存在而LHS中不存在的强盘软冷却发射造成的。

英文摘要:

We discuss the origin of the dramatically different X-ray spectral shapes observed in the Low Hard State (LHS: dominated by thermal comptonisation) and the High Soft State (HSS: dominated by the accretion disc thermal emission and non-thermal comptonisation in the corona). We present numerical simulations using a new code accounting for the so-called synchrotron boiler effect. These numerical simulations when compared to the data allow us to constrain the magnetic field and temperature of the hot protons in the corona. For the hard state of Cygnus X-1 we find 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). On the other hand, our results also point toward proton temperatures that are substantially lower than typical temperatures of the ADAF models. Finally, we show that in both spectral states Comptonising plasma could be powered essentially through power-law acceleration of non-thermal electrons, which are then partly thermalised by the synchrotron and Coulomb boiler. This suggests that, contrary to current beliefs, the corona of the HSS and that of the LHS could be of very similar nature. The differences between the LHS and HSS coronal spectra would then be predominantly caused by the strong disc soft cooling emission which is present in the HSS and absent in the LHS.

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