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arXiv 0812.3358astro-ph
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朱雀双星Gamma-Ray LS 5039 X射线辐射的光谱和时间特性研究

Study of the Spectral and Temporal Characteristics of X-Ray Emission of the Gamma-Ray Binary LS 5039 with Suzaku

T. Takahashi, T. Kishishita, Y. Uchiyama, T. Tanaka, K. Yamaoka, D. Khangulyan, F. A. Aharonian, V. Bosch-Ramon, J. A. Hinton

摘要:

我们报告的结果,从朱雀宽频带X射线观测银河系双星源LS 5039。朱雀星的数据连续覆盖了一个以上的轨道周期,显示出在这个TeV伽马射线发射系统的轨道周期上X射线发射的强烈调制。X射线发射在轨道相位~ 0.1处显示出最小值,接近于紧凑天体的所谓上合,在相位~0.7处显示出最大值,非常接近于紧凑天体的下合。直到70 keV的X射线光谱数据由具有在γ ~1.45 - 1.61范围内变化的相位相关光子指数的硬幂律描述。通量变化的幅度是2.5倍,但明显小于TeV通量变化的8倍。除此之外,两条光变曲线相似,但不完全相同。虽然在许多星系双星系统中发现了周期性的X射线发射,但朱雀号的结果意味着一种与X射线的“标准”起源不同的现象,这种X射线的起源与在致密伴星周围形成的热吸积等离子体的发射有关。LS 5039的X射线辐射可能与极高能量的电子有关,而极高能量的电子也是导致TeV伽马射线辐射的原因。伽马射线是电子对可见恒星光子的逆康普顿散射的结果,而X射线是通过同步辐射产生的。然而,虽然TeV伽马射线信号的调制可以自然地由光子-光子对产生和各向异性逆康普顿散射来解释,但观察到的同步加速器X射线的调制需要一个额外的过程,最自然的是辐射产生区域的绝热膨胀。

英文摘要:

We report on the results from Suzaku broadband X-ray observations of the galactic binary source LS5039. The Suzaku data, which have continuous coverage of more than one orbital period, show strong modulation of the X-ray emission at the orbital period of this TeV gamma-ray emitting system.The X-ray emission shows a minimum at orbital phase ~ 0.1, close to the so-called superior conjunction of the compact object, and a maximum at phase ~0.7, very close to the inferior conjunction of the compact object. The X-ray spectral data up to 70 keV are described by a hard power-law with a phase-dependent photon index which varies within Gamma ~1.45 - 1.61. The amplitude of the flux variation is a factor of 2.5, but is significantly less than that of the factor ~8 variation in the TeV flux. Otherwise the two light curves are similar, but not identical. Although periodic X-ray emission has been found from many galactic binary systems, the Suzaku result implies a phenomenon different from the "standard" origin of X-rays related to the emission of the hot accretion plasma formed around the compact companion object. The X-ray radiation of LS5039is likely to be linked to very-high-energy electrons which are also responsible for the TeV gamma-ray emission. While the gamma-rays are the result of inverse Compton scattering by electrons on optical stellar photons, X-rays are produced via synchrotron radiation. Yet, while the modulation of the TeV gamma-ray signal can be naturally explained by the photon-photon pair production and anisotropic inverse Compton scattering, the observed modulation of synchrotron X-rays requires an additional process, the most natural one being adiabatic expansion in the radiation production region.

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