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arXiv 2402.15067astro-ph.HE
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磁星作为AT2018cow的中心引擎:光学、软X射线与硬X射线辐射

Magnetar as the Central Engine of AT2018cow: Optical, Soft X-Ray, and Hard X-Ray Emission

Long Li, Shu-Qing Zhong, Di Xiao, Zi-Gao Dai, Shi-Feng Huang, Zhen-Feng Sheng

AI总结:

本文提出以毫秒磁星为中心引擎的双区模型,通过条纹磁星风磁耗散光子泄漏及抛射物热化,成功解释AT2018cow的光学、软X射线和硬X射线辐射及能谱,并约束其抛射物质量、速度与磁星参数。

摘要:

AT2018cow是迄今为止观测最广泛、研究最深入的快变蓝色光学暂现源;其独特的观测性质对现有所有标准模型构成挑战。本文采用以磁星为中心引擎的模型,对AT2018cow的光学、软X射线和硬X射线辐射的光度演化以及X射线能谱进行建模。我们考虑一个双区模型:内部为条纹磁星风,外部为膨胀抛射物。AT2018cow的软X射线和硬X射线辐射可由条纹磁星风内部渐进磁耗散产生的高能光子泄漏来解释,而明亮的紫外/光学热辐射则源于被俘获光子对抛射物的热化作用。我们的模型给出的双分量能谱,由风中光学厚区域的准热成分叠加在光学薄同步辐射成分上构成,很好地重现了AT2018cow的X射线能谱形状。马尔可夫链蒙特卡洛拟合结果表明,为解释热光学辐射极短的上升至峰值时间,需要较低的抛射物质量$M_{\rm ej}\approx0.1~M_\odot$和较高的抛射物速度$v_{\rm SN}\approx0.17c$。需要一个初始周期$P_0\approx3.7~\rm ms$、表面磁场$B_p\approx2.4\times10^{14}~\rm G$的毫秒磁星作为AT2018cow的中心引擎。

英文摘要:

AT2018cow is the most extensively observed and widely studied fast blue optical transient to date; its unique observational properties challenge all existing standard models. In this paper, we model the luminosity evolution of the optical, soft X-ray, and hard X-ray emission, as well as the X-ray spectrum of AT2018cow with a magnetar-centered engine model. We consider a two-zone model with a striped magnetar wind in the interior and an expanding ejecta outside. The soft and hard X-ray emission of AT2018cow can be explained by the leakage of high-energy photons produced by internal gradual magnetic dissipation in the striped magnetar wind, while the luminous thermal UV/optical emission results from the thermalization of the ejecta by the captured photons. The two-component energy spectrum yielded by our model with a quasi-thermal component from the optically thick region of the wind superimposed on an optically thin synchrotron component well reproduces the X-ray spectral shape of AT2018cow. The Markov Chain Monte Carlo fitting results suggest that in order to explain the very short rise time to peak of the thermal optical emission, a low ejecta mass $M_{\rm ej}\approx0.1~M_\odot$ and high ejecta velocity $v_{\rm SN}\approx0.17c$ are required. A millisecond magnetar with $P_0\approx3.7~\rm ms$ and $B_p\approx2.4\times10^{14}~\rm G$ is needed to serve as the central engine of AT2018cow.

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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