题目：The Transient Slim Disk of the Changing-look Active Galactic Nucleus 1ES 1927+654

报告人：李阮存（北京大学）

时间：2023年9月27日（周三）15:30

地点：紫金港西区海纳苑8幢323 

摘要：In changing-look active galactic nucleus (AGN) the optical-to-X-ray continuum flux typically increases significantly as broad emission lines appear. The changing-look AGN 1ES 1927+654, hosting already a highly accretion black hole, displays peculiar X-ray properties after its optical changing-look events in early 2018. We carried out a follow-up campaign to probe its extreme accretion physics, using 34 optical spectra, 800 NICER and 14 Swift/XRT observations, as well as 7 simultaneous XMM-Newton/NuSTAR exposures. Detailed spectral energy distribution analysis suggests that the black hole was accreting super-critically, with $t^{-5/3}$ declining mass accretion rate. The bolometric luminosity was logarithmically dependent on the mass accretion rate, suggesting the existence of a slim disk. After 0.55 solar masses of material was consumed, the evolution of the radiation efficiency and disk temperature suggest that the accretion flow finally returned to a thin disk. During the transient slim disk phase, the X-ray corona tightly correlated with the properties of the inner accretion flow, suggesting that the corona plasma originated from the disk itself. Additionally, the UV-X-ray spectral index and bolometric correction follow completely different branch during the slim disk phase. This study provides several important insights into the physical properties of slim disks and the AGN unified model.

个人简介：

Ruancun Li is currently a 5th-year PhD student at Peking University. He obtained his Bachelor's degree from the same institution in 2019, and continued onto his PhD studies under the supervision of Prof. Luis Chi Ho at the Kavli Institute for Astronomy and Astrophysics (KIAA).

欢迎老师和同学参加！