【3.25; Seminar】2026年粒子天体物理全国重点实验室系列学术报告 #8：模拟潮汐瓦解事件（TDE）的吸积过程与早期光变曲线/Simulating Accretion and Early Light Curve in Tidal Disruption Event (TDE)

时间/Time: 2026年3月25日周三上午10:00 / Wensday, March 25, 2026, 10:00 a.m.

地点/Location: 多学科楼229会议室 / Meeting Room 229, Multidisciplinary Building

报告人/Speaker: 黄小珊（加州理工学院）/ Xiaoshan HUANG (Caltech)

题目/Title: 模拟潮汐瓦解事件（TDE）的吸积过程与早期光变曲线 / Simulating Accretion and  Early Light Curve in Tidal Disruption Event (TDE)

主持人/Host: 冯骅 研究员 / Prof. Hua FENG

摘要/Abstract:

恒星靠近超大质量黑洞时会被黑洞的潮汐力撕碎，后续的吸积可以引发多波段的暂现耀发，是一类近十年快速发展的时域事件。目前，TDE的辐射起源还尚未明确，研究其辐射机制可以为理解超大质量黑洞的吸积提供关键依据。

本报告将讨论在TDE吸积盘形成过程中可能的辐射机制。我们用三维辐射流体力学数值模拟追踪了恒星碎片流从初始能量耗散后到回落率峰值后约一周的动力学演化。数值模拟的结果发信啊与简化的经典理论不同的是，恒星碎片的圆化并非瞬时完成的。在初始能量耗散约一个月后，高度圆化的吸积流才逐渐形成，该过程明显滞后于恒星碎片回落率的峰值。

我们同时发现圆化过程中的激波是TDE的主要辐射来源，其贡献超过了吸积过程本身。圆化过程中同时也抛射出一些恒星碎片，自发的形成的光学厚的介质。这样形成的光球层是不对称的，因此观测到的光变曲线与观测视角高度相关。通过改变观测角度，这些数值模拟可以复现x射线高亮度和低亮度的两类光学事件。

借助多波段的辐射转移模拟，我们推测了多波段光变曲线，并据此重构了宽波段光谱能量分布（SED）。在多个演化阶段中，光谱的能量峰值均位于极紫外波段，对应的光学与紫外测光结果与已观测TDE基本一致。模拟还显示，即使实际观测中，测光波段的能量全部低于处于极紫外的峰值，加入紫外波段测光数据能有效提升黑体温度的测量准确度。

The tidal disruption of a star by a supermassive black hole and consequent accretion can lead to a transient electromagnetic flare in multiple bands. However, the origin of the detected emission from such tidal disruption events (TDEs) remains an open question.

In this talk, I will discuss the potential emission mechanisms in TDEs during accretion disk formation, implied by series of 3D radiation-hydrodynamic simulations. We find that circularization of stellar debris is not prompt. A more circularized accretion flow only forms after about one month following the initial energy dissipation, lagging behind the fallback rate peak. 

The circularization shocks are an important emission source rather than accretion itself. Photons produced by shocks in the inner accretion flow are reprocessed by an optically thick layer formed during circularization. The photosphere is asymmetric, leading to angular-dependent light curves. By varying the viewing angle, we can reproduce optical events that are either X-ray bright or X-ray dim.

We also construct broad band broadband spectral energy distribution (SED) from simulations. At multiple epochs, the SED peaks in the extreme UV, producing optical and UV photometry that are overall consistent with observed TDEs. We also found including pre-peak UV photometry can improve blackbody temperature measurements.

个人简介/Biography:  

黄小珊，加州理工Burke Fellow博士后，于2023年在弗吉尼亚大学获得博士学位。主要研究方向包括流体力学数值模拟和辐射转移过程，近期研究兴趣是暂现天文源中的辐射机制，特别是与黑洞吸积相关的现象。

I obtained doctoral degree from University of Virginia in 2023, then joining Caltech as a Burke Fellow since then. I work on hydrodynamic simulations including radiation transfer processed. I am interested in understanding transient event driven by accretion and shock.