Abstract
X-ray reverberation is a proven technique capable of probing the innermost region of accretion disks around compact objects. Current theoretical effort assumes that the disk is geometrically thin, optically thick and rotating at Keplerian speed. Thus, these theoretical models cannot be applied to super-Eddington accretion systems because the thin disk approximation fails in this accretion regime. State-of-the-art numerical simulations of super-Eddington accretion show optically thick winds being launched from the geometrically and optically thick disks. Therefore, the reflection geometry of the super-Eddington case is morphologically different from the thin disk picture, and, thus, we need new theoretical methods to handle X-ray reverberation on super-Eddington accretors. In this probationary seminar of 25 minutes, I provide a detailed introduction to X-ray reverberation, so non-experts can use it as an introduction to this field. The main focus of the talk is a morphological comparison between the X-ray reverberation signal from the Fe K-alpha alpha line produced in super-Eddington and classical thin disks geometries. Here, I briefly present results from my previous paper, Thomsen et al. 2019, where we show the Fe line profiles produced are morphological different - with the super-Eddington reflection geometry producing substantially more blueshifted and symmetric line profiles. Also, I focus on new results where I have included the temporal aspect of the line profiles in the comparisons. These theoretical results of X-ray reverberation on super-Eddington accretors are consistent with the observed Fe K-alpha line from the jetted tidal disruption event, Swift J1644. A transient super-Eddington accretion disk is believed to have formed out of stellar debris after the tidal disruption event, Swift J1644. Lastly, I finish the talk by presenting the future aspect of my research and projects, such as extracting black hole parameters from observations and performing detailed radiative transfer on accretion disks to calculate the entire reflection spectrum and not just the Fe line.
Anyone interested is welcome to attend.