Nonthermal High-Energy Emission from Colliding Winds of Massive Stars
Nonthermal High-Energy Emission from Colliding Winds of Massive Stars
复制标题
大质量恒星碰撞风产生的非热高能辐射
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
O. Reimer
中科院分区：
文献类型：
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作者：
A. Reimer;A. Reimer;M. Pohl;O. Reimer
大质量恒星双星系统的碰撞风被认为是非热高能光子产生的潜在地点。受碰撞风场同步辐射探测的启发，我们研究了长周期WR+OB系统碰撞风中高能光子的产生特性。推导了定态质子和电子粒子谱的解析公式，假定粒子从热风粒子池中扩散加速，考虑绝热和所有相关的辐射损失，并包括对流/对流离开风碰撞区。这包括对Klein-Nishina过渡区中电子能量损失的解析近似。首次在CWB系统的背景下，我们的计算使用了全Klein-Nishina截面并考虑了逆康普顿散射过程的各向异性。这导致轨道流量的变化高达几个数量级，然而，这种变化可能会被系统的几何形状所模糊。各向异性和克莱因-西纳效应都可以在γ-射线域中产生特征光谱和变异性特征。由于传播效应导致对流为主区域的低能粒子不足，人们预计辐射光谱中会有印记。如果质子被加速到至少几个GeV，则可能会观察到π0衰变γ射线，这取决于注入的电子与质子的比率。我们表明，光子-光子对的产生通常是不可忽略的，潜在地影响到~50GeV以上的发射光谱，这取决于轨道相位和系统倾角。这些计算被应用于原型的WR+OB系统WR140和WR147，以预测它们的预期光谱和时间特性，并用当前和即将到来的γ-射线实验来评估它们的可探测性。
Colliding winds of massive star binary systems are considered as potential sites of nonthermal high-energy photon production. Motivated by the detection of synchrotron radio emission from the colliding wind location, we here investigate the properties of high-energy photon production in colliding winds of long-period WR+OB systems. Analytical formulae for the steady state proton- and electron-particle spectra are derived assuming diffusive particle acceleration out of a pool of thermal wind particles, taking into account adiabatic and all relevant radiative losses, and include advection/convection out of the wind collision zone. This includes analytical approximations for the electron energy losses in the Klein-Nishina transition regime. For the first time in the context of CWB systems, our calculations use the full Klein-Nishina cross section and account for the anisotropy of the inverse Compton scattering process. This leads to orbital flux variations by up to several orders of magnitude, which may, however, be blurred by the system's geometry. Both anisotropy and Klein-Nishina effects may yield characteristic spectral and variability signatures in the γ-ray domain. Since propagation effects lead to a deficit of low-energy particles in the convection-dominated zone, one expects imprints in the radiation spectra. If protons are accelerated to at least several GeV, π0-decay γ-rays might be observable, depending on the injected electron-to-proton ratio. We show that photon-photon pair production is generally not negligible, potentially affecting the emitted spectrum above ~50 GeV, depending on orbital phase and system inclination. The calculations are applied to the archetypal WR+OB systems WR 140 and WR 147 to predict their expected spectral and temporal characteristics and to assess their detectability with current and upcoming γ-ray experiments.