# 3D modelling of accretion disc in eclipsing binary system V1239 Her

## TL;DR

This paper presents 3D hydrodynamical simulations of accretion flow in the eclipsing binary V1239 Her, modeling the formation of the accretion disc and its light curve, which matches observations and explains variability.

## Contribution

The study introduces a realistic 3D simulation of accretion in V1239 Her, including hydrogen ionization and cooling, and successfully reproduces observed light curve features.

## Key findings

- Stationary accretion disc forms after ~15 orbital periods.
- Simulated light curves match observed eclipse profiles.
- Variations in accretion rate explain pre- and post-eclipse light curve changes.

## Abstract

We present the results of 3D-hydrodynamical simulations of accretion flow in the eclipsing dwarf nova V1239 Her in quiescence. The model includes the optical star filling its Roche lobe, a gas stream emanating from the inner Lagrangian point of the binary system, and the accretion disc structure. A cold hydrogen gas stream is initially emitted towards a point-like gravitational centre. A stationary accretion disc is formed in about 15 orbital periods after the beginning of accretion. The model takes into account partial ionization of hydrogen and uses realistic cooling function for hydrogen. The light curve of the system is calculated as the volume emission of optically thin layers along the line of sight up to the optical depth \tau =2/3 calculated using Planck-averaged opacities. The calculated eclipse light curves show good agreement with observations, with the changing shape of pre-eclipse and post-eclipse light curves being explained entirely due to ~ 50% variations in the mass accretion rate through the gas stream.