【12.7; Seminar】2024年粒子天体物理重点实验室系列学术报告 #57：Transient Slim Disk of the Changing-look AGN 1ES 1927+654

时间/Time: 12月7日上午10:00/ Saturday, December 7th at 10:00 a.m.

地点/Location: 多学科楼312会议室/Meeting Room 312, Multidisciplinary Building

报告人/Speaker: 李阮存/Ruancun Li (Peking University)

题目/Title: Transient Slim Disk of the Changing-look AGN 1ES 1927+654

主持人/Host: 李彦荣 研究员/Dr. Yanrong LI

Zoom在线会议号：85379617763，密码：333434

摘要/Abstract:

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. Photon trapping in the slim disk triggered by the high initial accretion rate was characterized by a low radiation efficiency (3%), which later more than doubled (8%) 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. Our work presents compelling observational evidence for the existence of slim accretion disks and elucidates the key parameters governing their behavior, paving the way for further exploration in this area.

个人简介/Bibliography:

Ruancun Li is currently a 6th-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 C. Ho at the Kavli Institute for Astronomy and Astrophysics (KIAA). His doctoral thesis is titled “Spectral Energy Distribution of Active Galactic Nuclei." Ruancun has extensive expertise in multiband SED modeling of AGNand is the author of a new astronomical data analysis tool named GALFITS.