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arXiv 1202.1386astro-ph.HE
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来自碰撞恒星风的X射线:紧密的WR +O双星系统的情况

X-rays from Colliding Stellar Winds: the case of close WR+O binary systems

Svetozar A. Zhekov

摘要:

我们已经分析了X射线发射的样品密切WR+O二进制使用的数据从公共钱德拉和XMM-牛顿档案。全局光谱拟合表明,需要双温等离子体来匹配来自这些物体的X射线发射,因为热分量(kT > 2 keV)是光谱模型的重要成分。在近距离的WR+O双星中,X射线很可能起源于由双星组成部分的巨大恒星风驱动的碰撞恒星风(CSW)激波。由于相互作用区域中等离子体的高密度,预计这些物体中的CSW冲击是辐射性的。与此相反,我们的分析表明,CSW激波在近距离WR+O双星样本是绝热的。只有当双星中恒星成分的质量损失率比目前公认的值至少小一个数量级时,这才是可能的。对于近距离WR+O双星的X射线特性,最可能的解释可能是它们的风是双分量流。质量更大的成分(密集的团块)对这些物体的光学/紫外线发射起作用,而光滑的稀薄成分是其X射线发射的关键因素。

英文摘要:

We have analysed the X-ray emission from a sample of close WR+O binaries using data from the public Chandra and XMM-Newton archives. Global spectral fits show that two-temperature plasma is needed to match the X-ray emission from these objects as the hot component (kT > 2 keV) is an important ingredient of the spectral models. In close WR+O binaries, X-rays likely originate in colliding stellar wind (CSW) shocks driven by the massive winds of the binary components. CSW shocks in these objects are expected to be radiative due to the high density of the plasma in the interaction region. Opposite to this, our analysis shows that the CSW shocks in the sample of close WR+O binaries are adiabatic. This is possible only if the mass-loss rates of the stellar components in the binary are at least one order of magnitude smaller than the values currently accepted. The most likely explanation for the X-ray properties of close WR+O binaries could be that their winds are two-component flows. The more massive component (dense clumps) play role for the optical/UV emission from these objects, while the smooth rarefied component is a key factor for their X-ray emission.

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