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arXiv 0808.4064astro-ph
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黑洞双星XTE J1817 -330外吸积盘中X射线的再处理

Reprocessing of X-rays in the outer accretion disc of the black hole binary XTE J1817--330

Marek Gierlinski, Chris Done, Kim Page

摘要:

我们建立了一个简单的模型的光学/紫外辐射的外光盘照射的内光盘和日冕发射的黑洞双星。我们将此应用到宽带雨燕数据从爆发的黑洞二进制XTE J1817- 330,以确认以前的结果,在软状态下的光学/紫外线发射是一致的再处理一个常数部分的热X射线光度。然而,这是非常令人惊讶的,因为盘温度在软状态下下降超过3倍,这应该在再处理效率中产生显著变化。最简单的方法来匹配所观察到的恒定的再处理部分是光盘皮肤高度电离(如30年前由van Paradijs建议的),这样大部分的光盘通量被反射,只有最硬的X射线加热光盘。恒定的再处理部分也有利于直接照明的光盘上的散射起源的光学深度/立体角的任何散射材料(风/日冕)在光盘应减少源光度下降。相比之下,当源进入硬态时,再处理的分数非常显著地增加(因子~6)。这种戏剧性的变化是不明显的X-射线/紫外线通量的相关性,因为它是由带通效应掩盖。然而,它不一定表示发射的变化,例如,喷射的出现主导了光学/UV通量,因为反射率必须随着光谱形状的急剧变化而变化。

英文摘要:

We build a simple model of the optical/UV emission from irradiation of the outer disc by the inner disc and coronal emission in black hole binaries. We apply this to the broadband Swift data from the outburst of the black hole binary XTE J1817--330 to confirm previous results that the optical/UV emission in the soft state is consistent with a reprocessing a constant fraction of the bolometric X-ray luminosity. However, this is very surprising as the disc temperature drops by more than a factor 3 in the soft state, which should produce a marked change in the reprocessing efficiency. The easiest way to match the observed constant reprocessed fraction is for the disc skin to be highly ionized (as suggested 30 years ago by van Paradijs), so that the bulk of the disc flux is reflected and only the hardest X-rays heat the disc. The constant reprocessed fraction also favours direct illumination of the disc over a scattering origin as the optical depth/solid angle of any scattering material (wind/corona) over the disc should decrease as the source luminosity declines. By contrast, the reprocessed fraction increases very significantly (by a factor ~6) as the source enters the hard state. This dramatic change is not evident from X-ray/UV flux correlations as it is masked by bandpass effects. However, it does not necessarily signal a change in emission e.g. the emergence of the jet dominating the optical/UV flux as the reflection albedo must change with the dramatic change in spectral shape.

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