Abstract AR Scorpii is a compact binary system which consists of a magnetic white dwarf and an M-type main sequence cool star. This binary system was discovered as a source of pulsating radiation in radio, infrared, optical, ultraviolet and X-ray wavebands. In this work, we have analyzed the γ-ray data in the energy range 100 MeV to 500 GeV from the Fermi-Large Area Telescope (LAT) observations for the period August 4, 2008 to March 31, 2019. The γ-ray emission from AR Scorpii over the last decade is not statistically significant and therefore 2σ upper limit on the integral flux above 100 MeV has been estimated. We reproduce the non-thermal broadband spectral energy distribution of AR Scorpii using an emission model having two synchrotron components due to the relativistic electrons in very high magnetic fields. The first component (Synchrotron-1) broadly describes the emissions at radio to high energy X-rays through the synchrotron radiation originating from a spherical region of radius ~ 1.8 × 1010 cm and a magnetic field strength of ~ 103 Gauss. The second component (Synchrotron-2) which reproduces the X-ray emission at lower energies and predicts the γ-ray emission, originates from another spherical region with radius ~ 1.4 × 1010 cm and a magnetic field strength of ~ 106 Gauss. The relativistic electron populations in both the emission regions are described by a smooth broken power law energy distribution. The γ-ray emission predicted by the Synchrotron-2 model is below the broadband sensitivity of the Fermi-LAT and is also consistent with the 95% confidence level upper limit on the integral flux above 100 MeV derived from more than 10 years of observations. According to our model, the binary system AR Scorpii could be a γ-ray source, although its emission level must be below the current detection limit of the Fermi-LAT.

中文翻译：

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模拟白矮星双星系统 AR Scorpii 的宽带发射

摘要 AR天蝎座是一个紧凑的双星系统，由一颗磁性白矮星和一颗M型主序冷星组成。这个双星系统被发现是无线电、红外线、光学、紫外线和 X 射线波段的脉动辐射源。在这项工作中，我们分析了 2008 年 8 月 4 日至 2019 年 3 月 31 日期间费米大面积望远镜 (LAT) 观测的 100 MeV 至 500 GeV 能量范围内的 γ 射线数据。来自过去十年的 AR Scorpii 在统计上并不显着，因此估计积分通量超过 100 MeV 的上限为 2σ。由于非常高磁场中的相对论电子，我们使用具有两个同步加速器组件的发射模型重现了 AR Scorpii 的非热宽带光谱能量分布。第一个组件（Synchrotron-1）广泛地描述了通过源自半径为 ~ 1.8 × 1010 cm 的球形区域和 ~ 103 高斯磁场强度的同步加速器辐射向高能 X 射线的无线电发射。第二个组件 (Synchrotron-2) 以较低的能量再现 X 射线发射并预测 γ 射线发射，源自另一个半径 ~ 1.4 × 1010 cm 和磁场强度 ~ 106 高斯的球形区域。两个发射区域中的相对论电子种群由平滑的破碎幂律能量分布描述。Synchrotron-2 模型预测的 γ 射线发射低于 Fermi-LAT 的宽带灵敏度，也与 10 多年观测得出的 100 MeV 以上积分通量的 95% 置信水平上限一致。根据我们的模型，双星系统 AR Scorpii 可能是一个 γ 射线源，尽管它的发射水平必须低于 Fermi-LAT 的当前检测极限。