The evolution stage and massive disc of the interacting binary V393 Scorpii

TL;DR

This study analyzes the binary system V393 Scorpii, revealing a stable stellar and disc configuration, a massive circumprimary disc, and its evolutionary history involving significant mass transfer, contributing to understanding of double periodic variables.

Contribution

It provides detailed physical parameters of V393 Scorpii, models the system's stable configuration, and links its evolution to specific mass transfer episodes and disc properties.

Findings

The orbital light curve remains stable during the long cycle.

A massive, optically thick disc surrounds the gainer star.

The system's evolution involved transferring 4 M_sun in 400,000 years.

Abstract

V393 Scorpii is a bright Galactic Double Periodic Variable showing a long photometric cycle of approx. 253 days. We present new VIJK photometric time series for V393 Scorpii along with the analysis of ASAS V-band photometry. We disentangled all light curves into the orbital and long cycle components. The ASAS V-band orbital light curve was modeled with two stellar components plus a circumprimary optically thick disc assuming a semidetached configuration. We present the results of this calculation, giving physical parameters for the stars and the disc, along with general system dimensions. Our results are in close agreement with those previously found by Mennickent et al. (2010) from IR spectroscopy and the modeling of the spectral energy distribution. The stability of the orbital light curve suggests that the stellar + disc configuration remains stable during the long cycle. Therefore, the long cycle should be produced by an additional variable and not-eclipsed emitting structure. We discuss the evolutionary stage of the system finding the best match with one of the evolutionary models of van Rensbergen et al. (2008). According to these models, the system is found to be after an episode of fast mass exchange that transferred 4 M_sun from the donor to the gainer in a period of 400.000 years. We argue that a significant fraction of this mass has not been accreted by the gainer but remains in an optically thick massive (about 2 M_sun) disc-like surrounding pseudo-photosphere whose luminosity is not driven by viscosity but probably by reprocessed stellar radiation. Finally, we provide the result of our search for Galactic Double Periodic Variables and briefly discuss the outliers beta Lyr and RX Cas.