学术活动

[colloquium] Fukun Liu: Elliptical accretion disk as a model for tidal disruption events

发布时间:2021-06-02
 
国台学术报告202107/NAOC Colloquium No.07 2021
暨国家天文台组建20周年学术报告Colloquium for the 20th anniversary of NAOC
   
报告题目/Title Elliptical accretion disk as a model for tidal disruption events 
报告人/Speaker Dr. Fukun Liu (KIAA-PKU)
报告时间/Time Wednesday 2:30 PM, June 02, 2021
报告地点/Location A601, NAOC & Live Streaming
主持人/Host Prof. Weimin Yuan
报告语言/Language: English (英文报告)
报告海报/Poster Click to download the poster
演示幻灯片/Slides Click to download the slides
报告视频/Video Click to watch the video (未经授权请勿转载)
直播链接/Live Webcast: [光明网直播地址]
https://topics.gmw.cn/2021-05/26/content_34877062.htm 
   
报告摘要/Abstract  
A star would be tidally disrupted, when it closely passes by a supermassive black hole (SMBH). After  the tidal disruption, about half of the stellar debris becomes bound and falls back to the SMBH. In the canonical model, the stellar debris circularizes rapidly to form a circular accretion disk of size about twice the orbital pericentre of the star. The circular accretion disk is hot with temperature about a few times 10^5 K and radiates mainly in the soft X-rays. Stellar tidal disruption events (TDEs) discovered in the X-rays are consistent with these expectations, but those in the optical/UV band are not. The observations of the luminous optical luminosities, sub-Eddington bolometric luminosities, low and constant blackbody temperature, large and decreasing emitting regions, and strong and complex asymmetric broad optical emissions of the optical/UV TDEs challenge the canonical model. We recently proposed and developed an elliptical accretion disk model for TDEs. We investigated the properties of the elliptical accretion disk and showed that the elliptical accretion disks have distinctive hydrodynamic structures and spectral energy distributions, which are fully consistent with the observations of optical/UV TDEs. In this talk, I will introduce the elliptical accretion disk model for TDEs and compare the predications with the observations of TDEs.
   
报告人介绍/Bio:  
Dr. Fukun Liu is a professor of astrophysics and the former director of the Department of Astronomy of Peking University and joint professor of KIAA-PKU. He is a member of the supervisors of the Chinese Astronomical Society. He obtained his PhD in astrophysics at SISSA (Italy) in 1999 and worked with Professor Marek Abramowicz at Chalmers University of Technology and Gothenburg University as a post-doctoral fellow of the Natural Science Research Foundation of Sweden (NFR fellow) from 1999 to 2001. He joined Peking University in 2001. His research interests include AGNs, accretion disk theory, supermassive black hole and binaries (SMBHBs), gravitational wave astrophysics, and tidal disruption events. Together with colleagues, he predicted the observational signatures and discovered the first pairs of SMBHBs in quiescent galaxies. His research group recently developed the elliptical accretion disk model for TDEs. He was awarded the Top 10 Achievements in Astronomy of China, respectively, in 2011 and 2014 and received the special allowances of the State Council of China in 2016.

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