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arXiv 1107.5100astro-ph.HE
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LMC X-1光谱变化的性质和原因

The Nature and Cause of Spectral Variability in LMC X-1

L. Ruhlen, D. M. Smith, J. Swank

摘要:

本文介绍了利用Rossi X射线定时探测器(RXTE)上的正比计数器阵列对河外风吸积黑洞X射线双星LMC X-1进行长期观测的结果。观测结果表明,LMC X-1的吸积盘具有反常的温光关系。我们使用深档案RXTE观测表明,整个温度-光度空间的大运动所占据的系统可以发生在短短半个小时的时间尺度。这些变化不能用从外盘传播的粘性时间尺度上的扰动来充分解释。相反,我们建议,明显的磁盘变化反映了快速波动的康普顿上散射日冕物质,掩盖了磁盘的内部。由变掩星模型导出的观测星盘光度和视星盘温度之间的关系定量地表明与观测结果吻合得很好。另外两个观测结果支持这一观点:幂律谱分量中的通量与拟合的内盘温度之间的逆相关,以及接近恒定的总光子通量,这表明当观测到较低的温度时,内盘不会被喷射。

英文摘要:

We present the results of a long-term observation campaign of the extragalactic wind-accreting black-hole X-ray binary LMC X-1, using the Proportional Counter Array on the Rossi X-Ray Timing Explorer (RXTE). The observations show that LMC X-1's accretion disk exhibits an anomalous temperature-luminosity relation. We use deep archival RXTE observations to show that large movements across the temperature-luminosity space occupied by the system can take place on time scales as short as half an hour. These changes cannot be adequately explained by perturbations that propagate from the outer disk on a viscous timescale. We propose instead that the apparent disk variations reflect rapid fluctuations within the Compton up-scattering coronal material, which occults the inner parts of the disk. The expected relationship between the observed disk luminosity and apparent disk temperature derived from the variable occultation model is quantitatively shown to be in good agreement with the observations. Two other observations support this picture: an inverse correlation between the flux in the power-law spectral component and the fitted inner disk temperature, and a near-constant total photon flux, suggesting that the inner disk is not ejected when a lower temperature is observed.

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