云南大学梦飞巡天望远镜对“元旦暴”GRB 250101A开展多波段同时观测并取得重要发现

Multiwavelength Analysis of "New Year's Burst" GRB 250101A with Mephisto Telescope

       2025年1月1日，空间望远镜Swift探测到来自110亿光年外的伽马射线暴GRB 250101A。伽马射线暴是宇宙中最剧烈的恒星级爆发现象，一次伽马射线暴在几秒钟内释放的能量，相当于太阳在其约100亿年一生中释放的总能量。其中持续时间超过2秒的长伽马射线暴起源于大质量恒星死亡，爆发产生的相对论性喷流与暴周介质相互作用，产生覆盖从射电、光学、X射线的多波段余辉，但这些余辉信号通常在爆发数分钟后便迅速衰减。作为宇宙中能量释放最高的爆发现象之一，伽马射线暴在瞬时辐射机制、余辉多样性、暴周环境性质等方面存在诸多的未解之谜。 

       云南大学梦飞巡天望远镜在GRB 250101A触发仅197秒后即启动了快速后随观测，凭借梦飞巡天望远镜独特的多波段同时高精度观测的能力，云南大学中国西南天文研究所梦飞团队对GRB 250101A余辉的产生机制和暴周环境进行了强有力的约束，发现在距离爆炸中心0.13pc处的暴周环境存在50%的密度跳变，并且光学余辉呈现出明显的消光特征，该项研究工作揭示了GRB 250101A前身星爆发前独特的暴周环境。

      梦飞巡天望远镜是云南大学“双一流”建设重大科研平台，是国际上首台大视场、大口径、多通道高精度成像巡天望远镜。其独特优势在于可同时在三个波段拍摄天体图像，提供超高精度测光及颜色数据。这次对“元旦暴”GRB 250101A的重要观测发现再次彰显了梦飞巡天望远镜在研究宇宙快速暂现源方面的独特优势。

      该工作目前已被国际知名天文期刊《天体物理学杂志》（ApJ）接受，预印本链接：https://arxiv.org/abs/2503.15805。云南大学中国西南天文研究所梦飞巡天望远镜项目团队成员杜国王博士为该论文的第一作者，杨元培副教授、张敬华副研究员、刘晓为教授，以及南京大学的杨俊博士为该项研究的通讯作者。该工作得到了国家重点研发计划、国家自然科学基金项目，以及云南省兴滇英才支持计划“顶尖团队”(202305AT350002)项目支持。

图1.梦飞巡天望远镜探测到的“元旦暴”GRB 250101A的早期多波段余辉。

Figure 1. Early multiband afterglow of the "New Year's Burst" GRB 2501101A detected by the Mephisto telescope.

    On January 1, 2025, the space telescope Swift detected Gamma-Ray Burst (GRB) 250101A, originating from 11 billion light-years away. GRBs are the most powerful stellar-scale explosions in the universe, with a single GRB releasing an amount of energy in just a few seconds equivalent to what our Sun will emit over its entire lifetime of approximately 10 billion years. Long GRBs, lasting more than two seconds, are believed to originate from the death of massive stars. The relativistic jets produced during these explosions interact with the surrounding circum-burst medium and further generate multi-wavelength afterglows in radio, optical, and X-ray bands. However, these afterglow signals typically decay rapidly after a few minutes. As one of the highest energy-releasing explosive phenomena in the universe, GRBs still hold many mysteries regarding their prompt emission mechanisms, afterglow diversity, and the nature of their circum-burst environments.

     Yunnan University's Mephisto telescope initiated rapid follow-up observations of GRB 250101A just 197 seconds after the trigger. Using Mephisto's unique capability for simultaneous, high-precision multi-wavelength observations, the Mephisto team at SWIFAR, Yunnan University placed strong constraints on both the afterglow's generation mechanism and the circum-burst environment of GRB 250101A. They discovered a 50% density jump in the circum-burst environment located 0.13 parsecs from the explosion center, and the optical afterglow showed clear extinction features. The study reveals the unique circum-burst environment of GRB 250101A before its explosion.

     The Mephisto telescope is a major scientific research platform developed under Yunnan University's "Double First-Class" initiative. It is the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. Its distinctive advantage lies in its ability to simultaneously capture object images in three different bands, providing high precision brightness and color data. This significant discovery concerning the "New Year's Burst" GRB 250101A once again highlights Mephisto's unique capabilities in studying fast cosmic transients.

    This work has been accepted for publication by The Astrophysical Journal (ApJ). The preprint is available at: https://arxiv.org/abs/2503.15805. Dr. Guowang Du, a member of the Mephisto team at SWIFAR, Yunnan University, is the first author of the paper. Associate Professor Yuan-Pei Yang, Associate Research Professor Jinghua Zhang, Professor Xiaowei Liu from SWIFAR, Yunnan University, and Dr. Yang Jun from Nanjing University are the corresponding authors of this research. This work was supported by the National Key Research and Development Program, the National Natural Science Foundation of China, and the “Top Team”of the “Yunnan Revitalization Talent Support Program” (202305AT350002).