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arXiv 2006.12950astro-ph.HE
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天蝎座AR白矮星双星宽带辐射的数值模拟

Modelling the broadband emission from the white dwarf binary system AR Scorpii

K. K. Singh, P. J. Meintjes, Q. Kaplan, F. A. Ramamonjisoa, S. Sahayanathan

摘要:

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\emph{Fermi} -大面积望远镜(LAT)观测的能量范围为100 MeV至500 GeV的$γ$射线数据。在过去的十年里,天蝎座AR的$γ$射线发射在统计上并不显著,因此估计了100 MeV以上积分通量的2 $σ$上限。我们再现的非热宽带光谱的能量分布的AR天蝎座使用的发射模型有两个同步加速器组件,由于相对论电子在非常高的磁场。第一部分(同步加速器-1)概括地描述了通过同步加速器辐射从半径为$\sim$ 1.8 $\times$ 10 $^{10}$ cm和磁场强度为$\sim$ 10 $^3$高斯的球形区域产生的射电到高能X射线的发射。第二个组成部分(同步加速器-2),它再现了较低能量的X射线发射,并预测$γ$ -射线发射,起源于另一个半径为$\sim$ 1.4 $\times$ 10 $^{10}$ cm和磁场强度为$\sim$ 10 $^6$高斯的球形区域。在两个发射区的相对论电子布居数描述了一个光滑的破幂律能量分布。由同步加速器-2模型预测的$γ$ -射线发射低于\emph{Fermi} -LAT的宽带灵敏度,并且也与从超过10年的观测中得出的100 MeV以上的积分通量的95 $\%$置信水平上限一致。根据我们的模型,天蝎座AR双星系统可能是一个$γ$射线源,尽管它的发射水平必须低于\emph{Fermi} -LAT的当前检测极限。

英文摘要:

In this work, we have analyzed the $γ$-ray data in the energy range 100 MeV to 500 GeV from the \emph{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 2$σ$ 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 $\sim$ 1.8$\times$10$^{10}$ cm and a magnetic field strength of $\sim$ 10$^3$ 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 $\sim$ 1.4$\times$10$^{10}$ cm and a magnetic field strength of $\sim$ 10$^6$ 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 \emph{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 \emph{Fermi}-LAT.

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