...
- 14.6., Kari Koljonen (IFY, NTNU): The origin of optical emission lines in the soft state of X-ray binary outbursts
Abstract: The optical emission line spectra of X-ray binaries are thought to be produced in an irradiated atmosphere, potentially the base of a wind, positioned above the outer accretion disc. However, the physical nature and conditions of the region that forms these lines are not well understood. In this presentation, I will discuss our study of X-ray binary MAXI J1820+070 in the soft state associated with its 2018 outburst. We modeled a line-rich, soft state, broadband spectrum using the X-Shooter instrument at the Very Large Telescope, with a Monte Carlo radiative transfer code that employed a simple biconical disc wind model. This model was inspired by radiation-hydrodynamic simulations of irradiation-driven outflows from X-ray binary discs. I will demonstrate that such a model can qualitatively replicate the observed features and that almost all of the optical emission in the model arises from the transonic "transition region" between the disc atmosphere and a thermally-driven wind. Our research shows that this transition region can be the source of the abundant optical lines seen in the soft state spectra of X-ray binaries during outburst events. These "wind bases" can also have a significant effect on the infrared-to-ultraviolet continua, and can even dominate the emission in the red part of the spectrum. Overall, the strong irradiation of the outer disc by the inner accretion flow can naturally create both the optical line-forming layer and an overlying outflow/atmosphere that generates X-ray absorption lines that are typically observed during the bright soft states of X-ray binary outbursts.
slides
- summer break
- 29.08. Benedikt Schroer (U Chicago): Transport of Galactic Cosmic-Ray Nuclei
Abstract: C....
slides
- 12.09. Vittoria Vecchiotti (IFY, NTNU Amanda Anlaug (NOT): H....
Abstract: C....
slides
- 0519.09.. Benedikt Schroer (U Chicago Vittoria Vecchiotti (IFY, NTNU): H....
Abstract: C....
slides
...