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arXiv 2209.02121astro-ph.HEphysics.plasm-ph
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含能磁体中的能量耗散和gamma-ray发射

Magnetic energy dissipation and gamma-ray emission in energetic pulsars

Hayk Hakobyan, Alexander Philippov, Anatoly Spitkovsky

摘要:

一些能量最高的恒星在$0.1$到$100$ GeV波段表现出旋转调制的伽马射线辐射。这种辐射的亮度通常是脉冲星自旋下降功率(伽马射线效率)的$0.1\text{-}10\%$,这意味着可用电磁能量的很大一部分在磁层中耗散,并作为高能光子重新辐射。为了研究这种现象,我们使用具有强同步加速器冷却的3D粒子模拟来模拟脉冲星磁层。我们特别关注的动态赤道电流片的磁重联和能量耗散发生。我们的模拟表明,磁层电流片中耗散的自旋下降功率的一小部分是由微物理等离子体尺度下的磁重联速率控制的,并且仅取决于脉冲星倾角。我们证明了加速对的最大能量和分布函数由电流片附近的每个粒子的可用磁能,磁化参数控制。等离子体分布的形状和程度被印在所观察到的同步辐射中,特别是在所观察到的光谱的峰值和截止处。我们研究了同步辐射冷却的强度如何影响所观察到的各种光谱形状。我们的结论很自然地解释了为什么具有更高自旋下降功率的恒星具有更宽的光谱形状,因此伽马射线效率较低。

英文摘要:

Some of the most energetic pulsars exhibit rotation-modulated gamma-ray emission in the $0.1$ to $100$ GeV band. The luminosity of this emission is typically $0.1\text{-}10\%$ of the pulsar spin-down power (gamma-ray efficiency), implying that a significant fraction of the available electromagnetic energy is dissipated in the magnetosphere and reradiated as high-energy photons. To investigate this phenomenon we model a pulsar magnetosphere using 3D particle-in-cell simulations with strong synchrotron cooling. We particularly focus on the dynamics of the equatorial current sheet where magnetic reconnection and energy dissipation take place. Our simulations demonstrate that a fraction of the spin-down power dissipated in the magnetospheric current sheet is controlled by the rate of magnetic reconnection at microphysical plasma scales and only depends on the pulsar inclination angle. We demonstrate that the maximum energy and the distribution function of accelerated pairs is controlled by the available magnetic energy per particle near the current sheet, the magnetization parameter. The shape and the extent of the plasma distribution is imprinted in the observed synchrotron emission, in particular, in the peak and the cutoff of the observed spectrum. We study how the strength of synchrotron cooling affects the observed variety of spectral shapes. Our conclusions naturally explain why pulsars with higher spin-down power have wider spectral shapes and, as a result, lower gamma-ray efficiency.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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