Lunch talk on Apr. 19, 2021

The Accretion Disk-Corona Systems in Super-Eddington Accreting AGNs

Speaker: Hezhen Liu (NJU)

Venue: Video conference

Time: 12:30 PM, Monday, Apr. 19, 2021

Abstract: 

Active galactic nuclei (AGNs) are powered by accretion onto central supermassive black holes (SMBHs), during which the gravitational potential energy of gas is converted to strong electromagnetic radiation. A considerable fraction of the energy is emitted in the X-ray band, generated from the hot accretion-disk corona surrounding the SMBHs. Although X-ray emission is a universal property of AGNs, our research group has found a small number of AGNs exhibiting weak X-ray emission compared to the expectation from their UV/optical emission. Some of them sometimes return to high states with nominal X-ray fluxes, thus showing extreme X-ray variability. These phenomena suggest possible unusual physical processes in the central engine or obscuration of X-ray emission by the surrounding medium in these AGNs, probably related to an unusual accretion process (e.g., super-Eddington accretion). In order to explore if super-Eddington accreting AGNs show unusual properties in terms of the X-ray coronae and accretion disk-corona connections, we investigate systematically for the first time the X-ray and multiwavelength properties of an AGN sample with reverberation-mapping measurements that provide relatively accurate SMBH-mass and accretion-rate measurements. I will present in this talk the results of this study and the implications.

Report PPT:  SWIFAR_Hezhen Liu.pdf