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arXiv 1505.03411astro-ph.SR
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具有大质量成分的双星风的X射线辐照

X-ray irradiation of the winds in binaries with massive components

Jiri Krticka, Jiri Kubat, Iva Krtickova

摘要:

具有热质量成分的双星是强X射线源。除了个别双星的内在X射线辐射来源于它们的风之外,X射线辐射还来源于致密伴星的吸积或风的碰撞。由于热星风是由重元素谱线中的光吸收驱动的,因此风的加速对电离状态很敏感。因此,由外部X射线源引起的过电离强烈地影响单个部件的风。我们研究了外部X射线辐照对热星风的影响。我们使用我们的动力学平衡(NLTE)风模型来估计外部X射线电离的影响,不同的X射线亮度和源距离。该模型计算O型星的典型参数。X射线的影响由X射线亮度、给定点与X射线源之间的光学深度以及到X射线源的距离给出。因此,可以用X射线光度与~(10)的关系图来解释这一结果。光学深度参数。在低X射线光度或离X射线源很远的双星中,X射线是可以忽略的。对于较高的X射线亮度和更接近X射线源,X射线的影响更强。存在一个X射线亮度高、光学厚度参数低的禁区,在此区域内X射线电离导致风的抑制。在这些图中观测到的恒星的位置与我们的预测非常吻合。所有风力驱动的高质量X射线双星(HMXB)都位于禁区之外。它们中的许多靠近禁区的边界,表明它们的X射线亮度是自我调节的。我们讨论了我们的工作对其他二进制类型的影响。

英文摘要:

Binaries with hot massive components are strong X-ray sources. Besides the intrinsic X-ray emission of individual binary members originating in their winds, X-ray emission stems from the accretion on the compact companion or from wind collision. Since hot star winds are driven by the light absorption in the lines of heavier elements, wind acceleration is sensitive to the ionization state. Therefore, the over-ionization induced by external X-ray source strongly influences the winds of individual components. We studied the effect of external X-ray irradiation on hot star winds. We used our kinetic equilibrium (NLTE) wind models to estimate the influence of external X-ray ionization for different X-ray luminosities and source distances. The models are calculated for parameters typical of O stars. The influence of X-rays is given by the X-ray luminosity, by the optical depth between a given point and the X-ray source, and by a distance to the X-ray source. Therefore, the results can be interpreted in the diagrams of X-ray luminosity vs.~the optical depth parameter. X-rays are negligible in binaries with low X-ray luminosities or at large distances from the X-ray source. The influence of X-rays is stronger for higher X-ray luminosities and in closer proximity of the X-ray source. There is a forbidden area with high X-ray luminosities and low optical depth parameters, where the X-ray ionization leads to wind inhibition. There is excellent agreement between the positions of observed stars in these diagrams and our predictions. All wind-powered high-mass X-ray binary (HMXB) primaries lie outside the forbidden area. Many of them lie close to the border of the forbidden area, indicating that their X-ray luminosities are self-regulated. We discuss the implications of our work for other binary types.

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