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arXiv 0902.1526astro-ph.SR
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探测来自喷气驱动共生星MWC 560的X射线

Detection of X-rays from the jet-driving Symbiotic Star MWC 560

Matthias Stute, Raghvendra Sahai

摘要:

我们报告的X射线辐射的检测从喷气驱动共生星MWC 560。我们用XMM-牛顿观测了MWC 560,观测时间为36 k。我们用XSPEC拟合了EPIC pn、MOS 1和MOS 2仪器的光谱,并用XRONOS软件包检查了光变曲线。该光谱可以与来自光学薄的热等离子体的高度吸收的硬X射线分量、能量为6.1 keV的高斯发射线和较少吸收的软热分量相拟合。最佳的拟合得到的模型中,热的组件是由光学薄的热发射产生的等压冷却流的最高温度为61千电子伏,这可能是创建一个光学薄的边界层内的表面上的吸积与矮星。在MWC 560中探测到的硬组分的导出参数与CH Cyg,SS 7317,RT Cru和T CrB等类似天体非常一致,它们都形成了发射硬X射线的共生星的新子类。我们先前对MWC 560中的射流进行的数值模拟表明,它应该产生可检测的软X射线发射。我们推断所观察到的软组分的温度为0.17千电子伏,即低于预期从我们的模型。总的软X射线通量(即< 3 keV)比其诞生后不久(<0.3年)传播的喷流的预测值小100倍以上,但与预期值一致,因为它随年龄而减少。ROSAT上限也与这种下降相一致。我们发现非周期性或准周期性变化的时间尺度上的分钟和小时,但没有周期性的快速变化。所有的结果都与吸积白矮星的X射线发射和周围光学薄边界层的存在是一致的。

英文摘要:

We report the detection of X-ray emission from the jet-driving symbiotic star MWC 560. We observed MWC 560 with XMM-Newton for 36 ks. We fitted the spectra from the EPIC pn, MOS1 and MOS2 instruments with XSPEC and examined the light curves with the package XRONOS. The spectrum can be fitted with a highly absorbed hard X-ray component from an optically-thin hot plasma, a Gaussian emission line with an energy of 6.1 keV and a less absorbed soft thermal component. The best fit is obtained with a model in which the hot component is produced by optically thin thermal emission from an isobaric cooling flow with a maximum temperature of 61 keV, which might be created inside an optically-thin boundary layer on the surface of the accreting with dwarf. The derived parameters of the hard component detected in MWC 560 are in good agreement with similar objects as CH Cyg, SS7317, RT Cru and T CrB, which all form a new sub-class of symbiotic stars emitting hard X-rays. Our previous numerical simulations of the jet in MWC 560 showed that it should produce detectable soft X-ray emission. We infer a temperature of 0.17 keV for the observed soft component, i.e. less than expected from our models. The total soft X-ray flux (i.e. at < 3 keV) is more than a factor 100 less than predicted for the propagating jet soon after its birth (<0.3 yr), but consistent with the value expected due its decrease with age. The ROSAT upper limit is also consistent with such a decrease. We find aperiodic or quasi-periodic variability on timescales of minutes and hours, but no periodic rapid variability. All results are consistent with an accreting white dwarf powering the X-ray emission and the existence of an optically-thin boundary layer around it.

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