# 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.

## Key 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~=~$(6.50 \pm 0.19) \times 10^{-10}$.

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Source: https://tomesphere.com/paper/1705.05195