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arXiv 0901.1297astro-ph.HEastro-ph.SR
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大质量恒星碰撞风的高能模型的参数约束:事例WR 147

Parameter constraints for high-energy models of colliding winds of massive stars: the case WR 147

A. Reimer, O. Reimer

摘要:

我们探讨的能力,高能量的观测约束轨道参数的长周期大质量的双系统的逆康普顿模型在碰撞风环境中的作用。这对于(非常)长周期的双星来说尤其重要,因为它们的轨道参数通常很难从传统方法中得知,例如沃尔夫-拉叶(WR)双星系统WR 147的情况就是如此,其中最近已经提出了高能发射的整数和魔法上限。我们进行了一组自由量的参数研究,描述了尚未模糊约束的几何形状和各自的影响,非热高能辐射从WR 147。这些结果与最近获得的高能观测结果以及Fermi-LAT等同时代高能仪器的灵敏度有关。对于像WR 147这样具有足够长周期的双星,伽马射线的衰减不太可能在高能光谱中产生任何独特的特征。这使得各向异性逆康普顿散射成为唯一对相对于轨道平面的视线角敏感的过程,因此即使从不覆盖轨道的实质部分的观测也可以推导系统参数。只要粒子加速足够有效地允许通过逆康普顿散射产生GeV光子,我们的分析表明WR 147具有大的倾角。否则,对于低倾角,电子加速被约束为如这里所预期的效率较低。

英文摘要:

We explore the ability of high energy observations to constrain orbital parameters of long period massive binary systems by means of an inverse Compton model acting in colliding wind environments. This is particular relevant for (very) long period binaries where orbital parameters are often poorly known from conventional methods, as is the case e.g. for the Wolf-Rayet (WR) star binary system WR 147 where INTEGRAL and MAGIC upper limits on the high-energy emission have recently been presented. We conduct a parameter study of the set of free quantities describing the yet vaguely constrained geometry and respective effects on the non-thermal high-energy radiation from WR 147. The results are confronted with the recently obtained high-energy observations and with sensitivities of contemporaneous high-energy instruments like Fermi-LAT. For binaries with sufficient long periods, like WR 147, gamma-ray attenuation is unlikely to cause any distinctive features in the high-energy spectrum. This leaves the anisotropic inverse Compton scattering as the only process that reacts sensitively on the line-of-sight angle with respect to the orbital plane, and therefore allows the deduction of system parameters even from observations not covering a substantial part of the orbit. Provided that particle acceleration acts sufficiently effectively to allow the production of GeV photons through inverse Compton scattering, our analysis indicates a preference for WR 147 to possess a large inclination angle. Otherwise, for low inclination angles, electron acceleration is constrained to be less efficient as anticipated here.

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