Title: “Numerical simulation of a stable sub-Eddington accretion disk”

Seminar by Debora Lančová (Silesian University in Opava – Czech Republic, Nicolaus Copernicus Astronomical Center – Polish Academy of Sciences).

Wednesday 16th of March, 14:15 p.m.

Google Meet Link: https://meet.google.com/ots-rija-hyc

Abstract: “We have performed general relativistic radiative magneto-hydrodynamics (GRRMHD) simulations of stable accretion disks around a stellar-mass black hole with sub-Eddington mass accretion rates. The numerical solutions reveal an elevated vertical structure which is in contradiction with a standard analytical models. Above a dense and geometrically thin core of dimensionless thickness h/r ∼ 0.1 (with h the height and r the radius), resembling a classic thin accretion disc, a puffed up, optically and geometrically thick layer of lower density and h/r ∼ 1.0 is formed. We refer to this solution as the puffy disk. I will also present the observational properties of puffy disks, in particular the geometrical obscuration at higher observing inclinations of the inner area by the puffed up region, and collimation of radiation along the accretion disk spin axis. These effects may explain the apparent super-Eddington luminosity of some ultraluminous X-ray binaries. I will also present synthetic spectra of puffy disks, and show that they are qualitatively similar to Comptonized spectra of an analytical disk model. The puffy discs may correspond to X-ray binary systems in the intermediate spectral state with luminosities above 0.3 of the Eddington luminosity”.