发表机构
School of Astronomy and Space Sciences, University of Chinese Academy of Sciences; National Astronomical Observatories, Chinese Academy of Sciences; Department of Physics and Institute of Theoretical Physics, Nanjing Normal University; Shanghai Astronomical Observatory, Chinese Academy of Sciences; Department of Space, Earth and Environment, Chalmers University of Technology; INAF - Istituto di Radioastronomia（中国科学院大学天文与空间科学学院; 中国科学院国家天文台; 南京师范大学物理科学与技术学院/理论物理研究所; 中国科学院上海天文台; 查尔姆斯理工大学地球与环境空间系; 意大利国家天体物理研究所射电天文研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
针对TDE候选体AT 2019avd的长期射电耀发，本文提出弓形激波模型可解释大部分观测辐射，并探讨了晚期正向激波主导及参数演化等替代情景的可行性。
AI 中文摘要
单一抛射物与超大质量黑洞周围的星系核介质（CNM）相互作用产生的正向激波，被广泛用于解释潮汐瓦解事件（TDEs）的射电辐射。然而，最近的观测证据，如快速上升的射电辐射、双峰宽带谱能量分布以及晚期激波能量的下降，对这一图景提出了挑战。因此，人们提出了其他情景，包括由外流与稠密云团碰撞产生的弓形激波、晚期新抛射物的产生以及微观物理参数的变化。为了研究这些因素的作用，我们利用跨越五年多的射电数据集，分析了TDE候选体AT 2019avd的长期射电耀发，该候选体已通过中红外观测识别出尘埃。我们发现，弓形激波情景可以解释大部分观测到的射电辐射，而正向激波或涉及不同云团的额外弓形激波可能在晚期开始主导。然而，在允许微观物理参数演化和更复杂的CNM结构时，正向激波情景仍然可行。我们讨论了外流-CNM和外流-云团相互作用情景中剩余的矛盾。
英文摘要
Forward shocks produced by interactions between a single ejected blob and the circumnuclear medium (CNM) around a supermassive black hole are widely invoked to explain radio emission from tidal disruption events (TDEs). However, recent observational evidence such as rapidly rising radio emission, double-peaked broadband spectral energy distributions, and declining shock energies at late times poses challenges to this picture. Alternative scenarios have therefore been proposed, including bow shocks arising from outflows colliding with dense clouds, the production of new ejecta at late times, and variations in microphysical parameters. To investigate the roles of these factors, we analyze the long-lived radio flare of the TDE candidate AT 2019avd, for which dust has been identified through mid-infrared observations, using a radio dataset spanning more than five years. We find that a bow-shock scenario can account for the majority of the observed radio emission, while a forward shock, or an additional bow shock involving different clouds, may begin to dominate at late times. However, a forward-shock scenario remains viable when allowing for evolving microphysical parameters and more complex CNM structures. We discuss the remaining tensions in both the outflow-CNM and outflow-cloud interaction scenarios.
Comments22 pages, 11 figures. Accepted for publication in The Astrophysical Journal
