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arXiv 2108.01948astro-ph.HE
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来自发光和磁化恒星的高能辐射

High energy radiation from luminous and magnetized stars

W. Bednarek

摘要:

部分早型星具有强偶极磁场的特征,这种强偶极磁场被来自星表面的稠密风的外流所改变。在离地表一定距离处(阿尔芬半径以上),风驱动磁场进入偶极磁场赤道区的重联。我们建议,电子加速在这些重联地区可以负责有效的康普顿恒星辐射产生的伽马射线发射。我们调查的电子在赤道地区的磁层的传播,包括他们的平流与赤道风。同步加速器和IC光谱的计算假设的一个重要部分的风能转移到相对论电子。作为一个例子,我们考虑了明亮的强磁化恒星HD 37022($Θ^1$ Ori C)的参数。IC伽马射线发射预计将被检测到无论是在GeV的能量范围内的费米-LAT望远镜或在亚TeV的能量由切伦科夫望远镜阵列。然而,由于恒星风通常是随时间变化的,并且磁轴可以倾斜于恒星的旋转轴,因此伽马射线发射预计会随着恒星的旋转周期而变化,并且在更长的时间尺度上,随着磁场活动的恒星圈而变化。这些特征可以作为对所提出的单个发光恒星伽马射线发射设想的检验。

英文摘要:

A part of early type stars is characterised by strong dipole magnetic field that is modified by the outflow of dense wind from the stellar surface. At some distance from the surface (above the Alfven radius), the wind drives the magnetic field into the reconnection in the equatorial region of the dipole magnetic field. We propose that electrons accelerated in these reconnection regions can be responsible for efficient comptonization of stellar radiation producing gamma-ray emission. We investigate the propagation of electrons in the equatorial region of the magnetosphere by including their advection with the equatorial wind. The synchrotron and IC spectra are calculated assuming that a significant part of the wind energy is transferred to relativistic electrons. As an example, the parameters of luminous, strongly magnetized star HD 37022 ($Θ^1$ Ori C) are considered. The IC gamma-ray emission is predicted to be detected either in the GeV energy range by the Fermi-LAT telescope or in the sub-TeV energies by the Cherenkov Telescope Array. However, since the stellar winds are often time variable and the magnetic axis can be inclined to the rotational axis of the star, the gamma-ray emission is expected to show variability with the rotational period of the star and, on a longer time scale, with the stellar circle of the magnetic activity. Those features might serve as tests of the proposed scenario for gamma-ray emission from single, luminous stars.

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