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arXiv 1412.8167astro-ph.HE
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单区域模型之外的Gamma-ray二进制文件:LS 5039的应用

Gamma-ray binaries beyond one-zone models: an application to LS 5039

Santiago del Palacio, Valentí Bosch-Ramon, Gustavo E. Romero

摘要:

背景:几个大质量恒星的双星系统存在伽马射线辐射。在大多数这些系统中,尽管有详细的观测资料,但对发射体的性质和结构仍然知之甚少。目的:我们调查的有效性,所谓的一个区域近似的高能量发射体的双星系统托管一个大质量的恒星。特别是,LS 5039的情况下考虑。研究方法:假设一个点状发射体处于静止状态,附近存在一颗大质量恒星,观测到的MeV和GeV通量作为参考,一个非热轻子模型被系统地应用于不同的位置,磁场,和非辐射损失。这使我们能够识别与观测最兼容的发射器配置以及模型预测与可用数据之间的不一致。结果:在LS 5039的情况下,最佳参数组合是快速非辐射冷却和低磁场。然而,出现差异时,在MeV和GeV的能量范围内与观测到的通量的模型结果进行比较。当分析中包括轨道运动时,预测失败,因为需要太大的发射器和能量预算。在这种情况下,沿着轨道的一半,预测X射线和TeV通量的值太高。结论:我们发现LS 5039的辐射并不是来自单一的电子群,发射极可能是扩展的,并且在低磁场下是不均匀的。我们认为,发射器移动相对论速度与多普勒助推起着重要的作用。关键词。恒星:大质量,X射线:双星,伽马射线:双星

英文摘要:

Context: Several binary systems hosting massive stars present gamma-ray emission. In most of these systems, despite detailed observational information being available, the nature and the structure of the emitter are still poorly known. Aims: We investigate the validity of the so-called one-zone approximation for the high-energy emitter in binary systems hosting a massive star. In particular, the case of LS 5039 is considered. Methods: Assuming a point-like emitter at rest, the presence of a nearby massive star, and the observed MeV and GeV fluxes as a reference, a non-thermal leptonic model is systematically applied for different locations, magnetic fields, and non-radiative losses. This allows us to identify both the emitter configurations that are most compatible with observations and inconsistencies between model predictions and the available data. Results: In the case of LS 5039, the best parameter combination is fast non-radiative cooling and a low magnetic field. However, discrepancies appear when comparing the model results at the MeV and GeV energy ranges with the observed fluxes. Predictions fail when the orbital motion is included in the analysis, because emitters and energy budgets that are too large are required. Values of X-ray and TeV fluxes that are too high are predicted in such a case, along half of the orbit. Conclusions: We show that the radiation in LS 5039 does not come from only one electron population, and the emitter is likely extended and inhomogeneous with a low magnetic field. We suggest that the emitter moves at relativistic velocities with Doppler boosting playing a significant role. Key words. Stars: high-mass, X-rays: binaries, gamma-rays: binaries

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