Cyclic light variations and accretion disk evolution in the LMC eclipsing binary OGLE-LMC-DPV-062

TL;DR

This study analyzes 32 years of photometric data of the LMC eclipsing binary OGLE-LMC-DPV-062, revealing long-term accretion disk variability and its impact on system evolution.

Contribution

It models the accretion disk's long-cycle variability and assesses the system's evolutionary state using combined photometric data and stellar evolution simulations.

Findings

Orbital period of 6.904858 days and a long cycle of 229.7 days identified.

Disk vertical extent varies significantly, affecting brightness and star obscuration.

Mass transfer rates correlate with the long cycle, influencing disk structure.

Abstract

Many intermediate-mass close binaries exhibit photometric cycles longer than their orbital periods, likely related to accretion-disk variability. Previous studies indicate that historical light curves (LC) provide key constraints on disk evolution and may help trace mass-transfer changes in these systems. We investigate the short- and long-term variability of the eclipsing system OGLE-LMC-DPV-062, with special emphasis on the long cycle. Our aims are to clarify the role of the accretion disk in these modulations, particularly on timescales of hundreds of days, and to determine the evolutionary state of the system in order to better understand its stellar components. We analyzed 32.3 years of photometric time series from OGLE in the I and V bands, and from MACHO in the BM and RM bands. Using data from multiple epochs, we modeled the accretion disk at 20 equally spaced phases of the long cycle. To solve the inverse problem, we applied an optimized simplex algorithm to derive the best-fitting parameters of the stars, orbit, and disk. The MESA code was used to assess the evolutionary stage of the system and predict its past and future evolution. We find an orbital period of 6.904858(15) d and a long cycle of 229.7 d. The orbital solutions reproduce the LC, but the quasi-conservative mass-transfer scenario yields rates too high to be compatible with the observed orbital-period stability. We find consistency with the observed orbital-to-long-period ratio under the magnetic dynamo hypothesis. The normalized mass-transfer rate follows the long cycle, reaching a maximum at minimum brightness. At that phase, the inner disk edge thickens, obscuring a larger fraction of the gainer star. Disk variability occurs mainly in its vertical extent, with a standard deviation of 69% of the mean value at the inner border, whereas changes in outer radius and temperature are smaller, 7% and 5%, respectively.