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arXiv 2103.00995astro-ph.HE
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gamma-ray双星的相对论流体模拟。II。适用于LS 5039

Relativistic fluid modelling of gamma-ray binaries. II. Application to LS 5039

David Huber, Ralf Kissmann, Olaf Reimer

摘要:

上下文本文提出了一个脉冲星风驱动下伽玛射线双星非热辐射的数值模型。目标。我们将这个模型应用到观测最好的伽马射线双星之一,LS 5039系统。方法.该模型涉及的脉冲星和恒星风的相互作用和电子对的运输从脉冲星风加速在新兴的冲击结构的联合模拟。我们计算的同步辐射和逆康普顿发射的后处理步骤,同时始终占相对论光束和$γγ$吸收恒星辐射场。结果恒星和脉冲星风的相互作用导致形成一个扩展的,不对称的风碰撞区域发展强烈的冲击,湍流混合,并在湍流二次冲击。碰撞区域的结构和由此产生的粒子分布都显示出显著的轨道变化。在弓形脉冲星风和科里奥利激波的粒子加速旁边,该模型自然地考虑了二次激波的粒子再加速,这有助于发射极高能(VHE)伽马射线。该模型成功地再现了LS 5039的主要光谱特征。虽然预测的光变曲线在高能量和VHE伽马射线波段与观测结果吻合良好,我们的模型仍然没有再现X射线到低能量伽马射线的调制,这是我们归因于所采用的磁场模型。结论.我们成功地模拟了观测到的LS 5039的多波段非热辐射的主要光谱特征,从而进一步证实了伽马射线双星的风驱动解释。开放的问题涉及到同步加速器调制,这可能是通过我们的模型的磁流体动力学扩展来解决。

英文摘要:

Context. We have presented a numerical model for the non-thermal emission of gamma-ray binaries in a pulsar-wind driven scenario. Aims. We apply this model to one of the best-observed gamma-ray binaries, the LS 5039 system. Methods. The model involves a joint simulation of the pulsar- and stellar-wind interaction and the transport of electronic pairs from the pulsar wind accelerated at the emerging shock structure. We compute the synchrotron and inverse Compton emission in a post-processing step, while consistently accounting for relativistic beaming and $γγ$-absorption in the stellar radiation field. Results. The stellar- and pulsar-wind interaction leads to the formation of an extended, asymmetric wind collision region developing strong shocks, turbulent mixing, and secondary shocks in the turbulent flow. Both the structure of the collision region and the resulting particle distributions show significant orbital variation. Next to the acceleration of particles at the bow-like pulsar wind and Coriolis shock the model naturally accounts for the reacceleration of particles at secondary shocks contributing to the emission at very-high-energy (VHE) gamma-rays. The model successfully reproduces the main spectral features of LS 5039. While the predicted lightcurves in the high-energy and VHE gamma-ray band are in good agreement with observations, our model still does not reproduce the X-ray to low-energy gamma-ray modulation, which we attribute to the employed magnetic field model. Conclusions. We successfully model the main spectral features of the observed multiband, non-thermal emission of LS 5039 and thus further substantiates a wind-driven interpretation of gamma-ray binaries. Open issues relate to the synchrotron modulation, which might be addressed through a magnetohydrodynamic extension of our model.

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