Non-LTE Modelling of the Structure and Spectra of the Hot Accretion Spots on the Surface of Young Stars

TL;DR

This paper models the structure and spectra of hot accretion spots on young stars, considering non-LTE effects for hydrogen and helium, revealing significant Stark broadening and minimal impact from carbon and oxygen departures.

Contribution

It introduces a non-LTE modelling approach for hot spots on young stars, accounting for gas pressure effects and spectral line broadening.

Findings

Hydrogen lines exhibit Stark broadening up to 1000 km/s.

Departures from LTE for carbon and oxygen have negligible impact.

Ram pressure influences the spectral line profiles significantly.

Abstract

The paper describes the modelling of the structure and spectra of the hot accretion spots on the surface of young stars with taking into account departures from LTE for hydrogen and helium. It has been found that the existence of the ram pressure of the in-falling gas at the outer boundary of the hot spot leads to the Stark broadening of the hydrogen line profiles up to FWHM of about 1000 km/s at the considered accretion parameters. It is shown that taking into account departures from LTE for atoms and ions of carbon and oxygen does not lead to noticeable changes in the structure of the hot spot.