Orbital Solutions and Absolute Elements of the W UMa Binary MW Pavonis

TL;DR

This study provides a detailed analysis of the W UMa binary MW Pavonis, revealing its overcontact state, component masses, radii, temperature, and period change, through combined photometric and radial velocity data.

Contribution

First comprehensive orbital and physical parameter determination of MW Pavonis using multi-source photometry and radial velocities, including spot modeling and period variation analysis.

Findings

MW Pavonis is an overcontact binary with both stars exceeding their Roche lobes.

Component masses are approximately 1.514 and 0.327 solar masses.

The orbital period is increasing at a rate of 6.50 x 10^-10.

Abstract

We present differential $UBV$ photoelectric photometry obtained by Williamon of the short-period A-type W~UMa binary MW~Pav. With the Wilson-Devinney analysis program we obtained a simultaneous solution of these observations with the $UBV$ photometry of Lapasset (1977,1980), the $V$ measurements by the $ASAS$ program, and the double-lined radial velocity measurements of Rucinski & Duerbeck (2006). Our solution indicates that MW~Pav is in an overcontact state, where both components exceed their critical Roche lobes. We derive masses of $M_1 = 1.514 \pm 0.063 \, M_\sun$ and $M_2 = 0.327 \pm 0.014 \, M_\sun$, and equal-volume radii of $R_1 = 2.412 \pm 0.034 \, R_\sun$ and $R_2 = 1.277 \pm 0.019 \, R_\sun$ for the primary and secondary, respectively. The system is assumed to have a circular orbit and is seen at an inclination of $86.39\arcdeg \pm 0.63\arcdeg$. The effective temperature of the primary was held fixed at $6900$~K, whereas the secondary's temperature was found to be $6969 \pm 10$~K. The asymmetry of the light curves requires a large, single star spot on the smaller, less massive secondary component. A consistent base solution, with different spot characteristics for the Williamon, Lapasset, and $ASAS$ data, was found. The modeled spot varied little during the 40-year range of photometric observations. The combined solution utilized a third light component and found that the period is changing at a rate of dP/dt~=~$(6.50 \pm 0.19) \times 10^{-10}$.