Life after eruption - II. The eclipsing old nova V728 Scorpii

TL;DR

This study re-examines the old nova V728 Sco, revealing it as an eclipsing system with unique variability and a large central object, providing insights into post-nova evolution and accretion processes.

Contribution

It is the first detailed analysis of V728 Sco as an eclipsing system, showing its orbital period, variability, and a large hot inner disc, advancing understanding of post-nova systems.

Findings

V728 Sco is an eclipsing system with a 3.32 h orbital period.

The central object is larger than a white dwarf, identified as a hot inner disc.

The system exhibits 'stunted' dwarf-nova-type outbursts.

Abstract

The old nova V728 Sco has been recently recovered via photometric and spectroscopic observations, 150 years after the nova eruption. The spectral properties pointed to a high-inclination system with a comparatively low mass-transfer rate. In this paper we show that the object is an eclipsing system with an orbital period of 3.32 h. It has enhanced long-term variability that can be interpreted as 'stunted' dwarf-nova-type outbursts. Using the ingress and egress times of the eclipsed components we calculate the radius of the central object. The latter turns out to be significantly larger than a white dwarf and we identify it with a hot inner disc. The implications for models on the behaviour of post-novae are discussed.