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arXiv 1106.4201astro-ph.HE
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轻子模型中耀变体硬甚高能谱的形成

Formation of hard very-high energy spectra of blazars in leptonic models

E. Lefa, F. M. Rieger, F. Aharonian

摘要:

TeV Blazar的VHE $γ$射线谱在对河外背景光(EBL)进行吸收修正后,出现异常的硬谱,这对传统的加速和辐射模型提出了挑战。我们调查的参数空间,允许生产这样的硬TeV光谱内的时间依赖轻子模型,无论是同步自康普顿(SSC)和外部康普顿(EC)的情况。在非常硬的$γ$ -射线光谱的解释的上下文中,时间相关的考虑变得至关重要,因为即使是非常硬的,初始电子分布可以显着变形,由于辐射能量损失。我们表明,非常陡峭的VHE谱可以避免,如果绝热损失被考虑在内。另一种在存在辐射损失的情况下保持极硬电子分布的方法是假设随机加速模型,该模型自然会导致稳态相对论性麦克斯韦型粒子分布。我们证明,在任何一种情况下轻子模型可以再现TeV光谱硬$E_γ dN/dE_γ \propto E_γ$。不幸的是,这在很大程度上限制了从耀变体的$γ$射线观测中提取EBL的潜力。

英文摘要:

The very high energy (VHE) $γ$-ray spectra of some TeV Blazars, after being corrected for absorption in the extragalactic background light (EBL), appear unusually hard, which poses challenges to conventional acceleration and emission models. We investigate the parameter space that allows the production of such hard TeV spectra within time-dependent leptonic models, both for synchrotron self-Compton (SSC) and external Compton (EC) scenarios. In the context of interpretation of very hard $γ$-ray spectra, time-dependent considerations become crucial because even extremely hard, initial electron distributions can be significantly deformed due to radiative energy losses. We show that very steep VHE spectra can be avoided if adiabatic losses are taken into account. Another way to keep extremely hard electron distributions in the presence of radiative losses, is to assume stochastic acceleration models that naturally lead to steady-state relativistic, Maxwellian-type particle distributions. We demonstrate that in either case leptonic models can reproduce TeV spectra as hard as $E_γ dN/dE_γ \propto E_γ$. Unfortunately this limits, to a large extend, the potential of extracting EBL from $γ$-ray observations of blazars.

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