发表机构
Tsinghua University（清华大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出EP260321a的快速X射线辐射源于延展星周物质中的激波突破，通过蒙特卡洛模拟和解析建模拟合出致密CSM参数，表明前身星在爆炸前数天发生了 episodic 质量损失，为恒星晚期演化提供新约束。
AI 中文摘要
爱因斯坦探针（Einstein Probe，EP）发现了一个快速X射线暂现源EP260321a，其光学对应体随后被归类为宽谱线Ic型超新星。其观测到的约690秒的上升时间与从Wolf-Rayet星（通常被视为剥离包层超新星的前身星）发生激波突破（shock breakout，SBO）的理论预测不符。在本文中，我们提出EP260321a起源于延展星周物质（circumstellar matter，CSM）内部的激波突破，其中突破光子最初被束缚，随后随着抛射物膨胀和不透明度降低而从未受激波的CSM中扩散出来。我们使用蒙特卡洛模拟和解析方法对该光子扩散过程进行建模，以描述温度演化。通过马尔可夫链蒙特卡洛采样，我们获得了最佳拟合的CSM参数：总CSM质量log10(Mcsm/Msun) = -3.3，CSM内半径Rin = 160 Rsun，CSM外半径Rout = 612 Rsun。如此致密CSM的存在表明，EP260321a的前身星在爆炸前仅数天经历了 episodic 质量损失，这为大质量恒星晚期演化提供了新的观测约束。
英文摘要
The Einstein Probe (EP) has discovered a fast X-ray transient, EP260321a, whose optical counterpart was subsequently classified as a broad-lined Type Ic supernova. Its observed rise time of about 690 seconds is inconsistent with theoretical predictions for shock breakout (SBO) from a Wolf-Rayet star, which is typically regarded as the progenitor of envelope-stripped supernovae. In this paper, we propose that EP260321a arose from a SBO within extended circumstellar matter (CSM), where breakout photons were initially trapped, then diffused out of the unshocked CSM as the ejecta expanded and the opacity decreased. We modeled this photon diffusion process using both Monte Carlo simulations and an analytical approach to describe the temperature evolution. Through Markov Chain Monte Carlo sampling, we obtain the best-fit CSM parameters of log10(Mcsm/Msun) = -3.3 for the total CSM mass, Rin = 160 Rsun for the inner CSM radius, and Rout = 612 Rsun for the outer CSM radius. The presence of such a dense CSM indicates that the progenitor of EP260321a underwent episodic mass loss just days before the explosion, providing new observational constraints on the late-stage evolution of massive stars.
CommentsAccepted for publication in ApJL
