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arXiv 0810.2035astro-ph
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银河系盘未分辨软X射线辐射的性质

The Nature of Unresolved Soft X-ray Emission from the Galactic Disk

K. Masui, K. Mitsuda, N. Y. Yamasaki, Y. Takei, S. Kimura, T. Yoshino, D. McCammon

摘要:

虽然在0.4 - 1 keV范围内约有40%的软X射线背景辐射来自河外,因此在中面方向上被银河吸收完全阻挡,但在中面方向上最多减少约20%。朱雀观测的方向,(1,b)=(235,0),显示OVII Ka发射强度与MBM-12的云朱雀观测,但揭示了一个狭窄的隆起峰值约0.9 keV。后一个分量部分地填补了中平面河外分量的减少。该特征可以很好地由具有约0.8keV的温度的薄的热发射来表示。由于在空间上扩展的热气体隐含着高压,因此发射很可能是未解决的微弱源的总和。我们认为很大一部分的发射来自暗淡的dM星。我们构建了一个模型光谱的空间未分辨的dM星,一贯解释所观察到的光谱和表面亮度。该模型还表明,dM星的辐射随b的增加而迅速减少,因此它不能完全补偿b ~ 2 - 10 deg时河外分量的减少。

英文摘要:

Although about 40% of the soft X-ray background emission in 0.4 to 1 keV range has extragalactic origins and thus is totally blocked by the Galactic absorption in midplane directions, it decreases at most by about 20 % in midplane. Suzaku observation of the direction, (l, b) = (235, 0), showed an OVII Kalpha emission intensity comparable with that of the MBM-12 on cloud Suzaku observation, but revealed a narrow bump peaked at ~ 0.9 keV. The latter component is partly filling the decrease of the extragalactic component in midplane. The feature can be well represented by a thin thermal emission with a temperature of about 0.8 keV. Because of the high pressure implied for spatially extended hot gas, the emission is likely a sum of unresolved faint sources. We consider a large fraction of the emission originates from faint dM stars. We constructed a model spectrum for spatially unresolved dM stars that consistently explains the observed spectrum and the surface brightness. The model also suggests that the emission from dM stars decreases very rapidly with increasing b, and thus that it cannot compensate entirely the decrease of the extragalactic component at b ~ 2 - 10 deg.

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