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arXiv 1312.0941astro-ph.HE
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发光黑洞X射线双星的陡幂律谱和高频准周期振荡模型

A model of the steep power law spectra and high-frequency quasi-periodic oscillations in luminous black hole X-ray binaries

Jason Dexter, Omer Blaes

摘要:

本文提出了一个新的发光黑洞X射线双星陡幂律态模型。该模型使用的事实是,在高光度下,辐射压力占主导地位的吸积盘的内径预计i)变得有效的光学薄和ii)产生显着的光度。因此,气体温度向内急剧上升,产生具有快速增加的峰值能量的局部饱和康普顿谱。这些频谱加在一起形成频谱的陡峭幂律尾部。给定的光子能量在这个尾巴对应于一个狭窄的半径范围,使本地垂直振荡的光盘自然产生高品质的高频准周期振荡(HFQPO)的硬X射线带。两个最低阶模式具有约1.53的鲁棒频率比。这个模型解释了陡峭的幂律谱和HFQPO在高光度下的出现,3:2的HFQPO频率比,以及它们与幂律谱分量的关系。我们预测当功率谱被限制在较窄的光子能带时,QPO品质因数会增加,而在较高的X射线能量或较低的亮度下,HFQPO频率会增加。未来的X射线望远镜可以从高阶模式中探测到更多的HFQPO。我们演示了如何使用这个模型来测量黑洞的自旋从HFQPO,并定性地估计GRO J1655-40的自旋为a/M ~ 0.4 - 0.7。

英文摘要:

We propose a new model of the steep power law state of luminous black hole X-ray binaries. The model uses the fact that at high luminosities, the inner radii of radiation pressure dominated accretion discs are expected to i) become effectively optically thin and ii) produce significant luminosities. The gas temperature therefore rises sharply inwards, producing local saturated Compton spectra with rapidly increasing peak energy. These spectra sum together to form a steep power law tail to the spectrum. A given photon energy on this tail corresponds to a narrow range in radius, so that local vertical oscillations of the disc naturally produce high quality high-frequency quasi-periodic oscillations (HFQPOs) in the hard X-ray band. The two lowest order modes have a robust frequency ratio of ~1.53. This model explains the appearance of steep power law spectra and HFQPOs at high luminosity, the 3:2 HFQPO frequency ratios, and their association with the power law spectral component. We predict an increase in QPO quality factor when the power spectrum is restricted to a narrower photon energy band, and an increase in HFQPO frequency at higher X-ray energies or lower luminosities. Future X-ray telescopes could detect additional HFQPOs from higher order modes. We demonstrate how this model could be used to measure black hole spin from HFQPOs, and qualitatively estimate the spin of GRO J1655-40 as a/M ~ 0.4 - 0.7.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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