Vertical Convection in Turbulent Accretion Disks and Light Curves of the A0620-00 1975 Outburst

TL;DR

This paper models the non-stationary alpha-disk with vertical convection and irradiation effects to explain the light curves of the 1975 A0620-00 outburst, estimating the turbulent viscosity parameter and explaining secondary luminosity features.

Contribution

It introduces a model incorporating vertical convection and irradiation in accretion disks, providing new insights into the light curve features of X-ray novae.

Findings

Estimated viscosity parameter alpha = 0.5-0.6.

Explained secondary luminosity maximum by matter injection.

Reproduced decay rate of luminosity during outburst.

Abstract

We present a model of the non-stationary $\alpha$-disk with account for the irradiation and the vertical convection in the outer accretion disk where hydrogen is partially ionized. We include the viscous energy generation in the mix-length convection equations in accretion disks. The optical and X-ray light curves of X-ray nova A0620-00 are investigated in terms of this model. The turbulent viscosity parameter of the accretion disk is estimated, $\alpha = 0.5 \div 0.6$, which is necessary to explain the luminosity decay rate on the descending branch of the X-ray light curve for the A0620-00 1975 outburst. The secondary luminosity maximum on the light curves is explained by assuming an additional injection of matter into the accretion disk from the optical companion.