Physical parameters and evolutionary route for the LMC interacting binary OGLE 05155332-6925581

TL;DR

This study combines light curves and spectroscopy to analyze the physical parameters and evolutionary stage of the LMC binary OGLE 05155332-6925581, revealing a mass transfer phase with a circumprimary disc and implications for angular momentum loss.

Contribution

It provides the first detailed physical and evolutionary characterization of OGLE 05155332-6925581, including a model of its circumprimary disc and mass transfer rate, advancing understanding of DPV systems.

Findings

System has a circumprimary optically thick disc with radius twice the star's.

Mass ratio of 0.21, with stellar masses 9.1 and 1.9 solar masses.

System is in a rapid mass transfer phase with a high transfer rate.

Abstract

We analyze multicolor light curves and high resolution optical spectroscopy of the eclipsing binary and Double Periodic Variable OGLE 05155332-6925581. According to Mennickent et al., this system shows a significant change in the long non-orbital photometric cycle, a loop in the color-magnitude diagram during this cycle and discrete spectral absorption components that were interpreted as evidence of systemic mass loss. We find that the best fit to the multi-band light curves requires a circumprimary optically thick disc with a radius about twice the radius of the more massive star. The spectroscopy indicates a mass ratio of 0.21+-0.02 and masses for the hot and cool stars of 9.1+-0.5 and 1.9+-0.2 M_sun, respectively. A comparison with synthetic binary-star evolutionary models indicates that the system has an age of 4.76E7 years, is in the phase of rapid mass transfer, the second one in the life of this binary, in a Case-B mass-exchange stage. Donor-subtracted H_alpha profiles show the presence of double emission formed probably in an optically thin circumstellar medium, while the variable HeI profile and the H_beta absorption wings are probably formed in the optically thick circumprimary disc. The model that best fit the observations shows the system with a relatively large mass transfer rate of dM/dt = 3.1E-6 M_sun/yr. However, the orbital period remains relatively stable during almost 15 years. This observation suggests that the hot-spot mass-loss model proposed by other authors is not adequate in this case, and that some other mechanism is efficiently removing angular momentum from the binary. Furthermore, our observations suggest that the DPV phenomenon could have an important effect in the balance of mass and angular momentum in the system.