Long photometric cycle and disk evolution in the $\beta$ Lyrae type binary OGLE-BLG-ECL-157529

TL;DR

This study investigates the long photometric cycle and disk evolution in the binary OGLE-BLG-ECL-157529, revealing variable disk properties and mass transfer linked to the long cycle in a Double Periodic Variable system.

Contribution

The paper presents the first detailed modeling of the light curve changes in OGLE-BLG-ECL-157529, linking them to variable disk structure and mass transfer in a DPV system.

Findings

The long cycle amplitude and length decrease over time.

Disk thickness and radius vary with the long cycle.

Changes in hot and bright spot temperatures and positions are observed.

Abstract

The subtype of hot algol semidetached binaries dubbed Double Periodic Variables (DPVs) are characterized by a photometric cycle longer than the orbital one, whose nature has been related to a magnetic dynamo in the donor component controlling the mass transfer rate. We aim to understand the morphologic changes observed in the light curve of OGLE-BLG-ECL-157529 that are linked to the long cycle. In particular, we want to explain the changes in relative depth of primary and secondary eclipses. We analyze $I$ and $V$-band OGLE photometric times series spanning 18.5 years and model the orbital light curve. We find that OGLE-BLG-ECL-157529 is a new eclipsing Galactic DPV of orbital period 24\fd8, and that its long cycle length decreases in amplitude and length during the time baseline. We show that the changes of the orbital light curve can be reproduced considering an accretion disk of variable thickness and radius, surrounding the hottest stellar component. Our models indicate changes in the temperatures of hot spot and bright spot during the long cycle, and also in the position of the bright spot. This, along with the changes in disk radius might indicate a variable mass transfer in this system.