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arXiv 1409.1679astro-ph.HE
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Sco X-1的硬X射线发射

Hard X-ray emission of Sco X-1

Mikhail G. Revnivtsev, Sergey S. Tsygankov, Eugene M. Churazov, Roman A. Krivonos

摘要:

利用INTEGRAL天文台研究了最亮的吸积中子星Sco X-1的硬X射线辐射。到目前为止,INTEGRAL已经收集了大约4毫秒的死区时间校正曝光。我们发现Sco X-1的硬X射线尾在能量~200-300 keV时均谱中呈幂律形状,没有截止。高能量截止的情况下不同意的模型,其中的尾巴形成作为一个结果的Comptonization的软种子光子对散装运动的物质附近的紧凑的对象的预测。尾部的振幅随时间变化,其系数大于10,最微弱的尾部位于其色-色图上所谓的耀斑分支的顶部。我们发现,当对应于光学厚吸积盘最里面部分的分量从发射光谱中消失时,记录到幂律尾的最小振幅。因此,我们认为硬X射线尾的存在可能与光学厚盘内部的存在有关。我们估计了这些高能电子的冷却时间,并表明它们不可能是热的。我们认为硬X射线尾辐射起源于软种子光子在电子上的康普顿上散射,它可能具有初始的非热分布。

英文摘要:

We study hard X-ray emission of the brightest accreting neutron star Sco X-1 with INTEGRAL observatory. Up to now INTEGRAL have collected ~4 Msec of deadtime corrected exposure on this source. We show that hard X-ray tail in time average spectrum of Sco X-1 has a power law shape without cutoff up to energies ~200-300 keV. An absence of the high energy cutoff does not agree with the predictions of a model, in which the tail is formed as a result of Comptonization of soft seed photons on bulk motion of matter near the compact object. The amplitude of the tail varies with time with factor more than ten with the faintest tail at the top of the so-called flaring branch of its color-color diagram. We show that the minimal amplitude of the power law tail is recorded when the component, corresponding to the innermost part of optically thick accretion disk, disappears from the emission spectrum. Therefore we show that the presence of the hard X-ray tail may be related with the existence of the inner part of the optically thick disk. We estimate cooling time for these energetic electrons and show that they can not be thermal. We propose that the hard X-ray tail emission originates as a Compton upscattering of soft seed photons on electrons, which might have initial non-thermal distribution.

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