We present results of a Chandra High-Energy Transmission Grating (HETG) observation of the carbon-rich Wolf-Rayet (WR) star WR 48a. These are the first high-resolution spectra of this object in X-ray. Blueshifted centroids of the spectral lines of ~ – 360 km s–1 and line widths of 1000-1500?km s–1 (FWHM) were deduced from the analysis of the line profiles of strong emission lines. The forbidden line of Si XIII is strong and not suppressed, indicating that the rarified 10-30 MK plasma forms far from strong sources of far-ultraviolet emission, most likely in a wind collision zone. Global spectral modeling showed that the X-ray spectrum of WR?48a suffered higher absorption in the 2012 October Chandra observation compared with a previous 2008?January XMM-Newton observation. The emission measure of the hot plasma in WR 48a decreased by a factor ~3 over the same period of time. The most likely physical picture that emerges from the analysis of the available X-ray data is that of colliding stellar winds in a wide binary system with an elliptical orbit. We propose that the unseen secondary star in the system is another WR star or perhaps a luminous blue variable.
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机译:我们介绍了钱德拉高能透射光栅(HETG)观察到的富含碳的Wolf-Rayet(WR)星WR 48a的结果。这些是该物体在X射线中的第一个高分辨率光谱。通过对强发射谱线的谱线分析得出了〜– 360 km s-1谱线的蓝移质心和1000-1500?km s-1(FWHM)的谱线宽度。 Si XIII的禁线很强,没有被抑制,这表明稀有的10-30 MK等离子体的形成远非强烈的远紫外线发射源,最有可能在风碰撞区。全球光谱建模表明,与2008年1月XMM-牛顿观测相比,2012年10月Chandra观测中WR?48a的X射线吸收光谱更高。在相同的时间段内,WR 48a中热等离子体的发射度量降低了约3倍。通过分析可用的X射线数据得出的最可能的物理图像是在椭圆轨道的宽双星系统中碰撞恒星风的图像。我们建议系统中看不见的次级恒星是另一个WR恒星,或者也许是发光的蓝色变量。
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