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arXiv 1807.01360astro-ph.HE
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从光变曲线直接了解低质量X射线双星的X射线辐射

Understanding X-ray Irradiation in Low-Mass X-ray Binaries directly from their Light-Curves

B. E. Tetarenko, G. Dubus, J. -P. Lasota, C. O. Heinke, G. R. Sivakoff

摘要:

在低质量X射线双星中观测到的周期性爆发的X射线光变曲线为约束(仍然)知之甚少的盘吸积过程提供了强有力的测试平台。这些光变曲线作为一个强有力的诊断,以探测驱动质量流入和流出这些双星系统的机制背后的物理。因此,我们开发了一种创新的方法,结合贝叶斯统计的基础,观察到的X射线光变曲线,吸积盘理论。用这种方法,我们的特征的角动量(和质量)的吸积盘的传输过程,以及X射线辐射加热的性质,调节从爆发最大值在低质量X射线瞬态的衰减。我们最近应用我们的方法,银河系黑洞低质量X射线二进制人口,从他们的光变曲线的$α$ -粘度参数在这些系统\citep{tetarenko2018}的首次定量测量。在本文中,我们继续研究这些双星,使用贝叶斯方法调查的X射线照射的光盘在爆发的强吸积。我们发现,盘不稳定性模型的预测,假设一个源的X射线照射成正比的中央吸积率在整个爆发,不足以描述BH-LMXB爆发光变曲线的后期阶段。我们假设,在整个人口中观察到的复杂和多变的光变曲线形态是在光盘内的时间和空间变化的照射,在整个个人的瞬态爆发的证据。最后,我们证明了我们的方法的鲁棒性,通过准确地再现的合成模型光曲线计算的数值代码建立在二进制系统中模拟吸积流。

英文摘要:

The X-ray light-curves of the recurring outbursts observed in low-mass X-ray binaries provide strong test beds for constraining (still) poorly understood disc-accretion processes. These light-curves act as a powerful diagnostic to probe the physics behind the mechanisms driving mass inflow and outflow in these binary systems. We have thus developed an innovative methodology, combining a foundation of Bayesian statistics, observed X-ray light-curves, and accretion disc theory. With this methodology, we characterize the angular-momentum (and mass) transport processes in an accretion disc, as well as the properties of the X-ray irradiation-heating that regulates the decay from outburst maximum in low-mass X-ray transients. We recently applied our methodology to the Galactic black-hole low-mass X-ray binary population, deriving from their lightcurves the first-ever quantitative measurements of the $α$-viscosity parameter in these systems \citep{tetarenko2018}. In this paper, we continue the study of these binaries, using Bayesian methods to investigate the X-ray irradiation of their discs during outbursts of strong accretion. We find that the predictions of the disc-instability model, assuming a source of X-ray irradiation proportional to the central accretion rate throughout outburst, do not adequately describe the later stages of BH-LMXB outburst light-curves. We postulate that the complex and varied light-curve morphology observed across the population is evidence for irradiation that varies in time and space within the disc, throughout individual transient outbursts. Lastly, we demonstrate the robustness of our methodology, by accurately reproducing the synthetic model light-curves computed from numerical codes built to simulate accretion flows in binary systems.

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