Light curve modeling of four short-period W UMa binaries

TL;DR

This study models four short-period W UMa contact binaries to estimate their parameters, revealing effects of magnetic activity and comparing photometric mass ratios with totally-eclipsing systems.

Contribution

It provides detailed modeling of four W UMa binaries near the period cutoff, including analysis of magnetic activity and assessment of photometric mass ratio reliability.

Findings

Three systems show light curve asymmetry due to magnetic activity.

Primaries are K-type, secondaries are M-type, and appear undersized and underluminous.

Photometric mass ratios are evaluated and compared with totally-eclipsing systems.

Abstract

We use extensive model grids to estimate the global parameters of four partially-eclipsing W UMa contact binaries near the period cutoff. All four systems consist of K-type main sequence primaries and M-type secondaries that appear undersized and underluminous for their masses because of the energy transfer through the common envelope. Three of the four stars exhibit light curve asymmetry that is explained in terms of magnetic activity and modeled with dark spots. We discuss the reliability of the photometric mass ratios and derived absolute parameters in context of total or partial eclipses and compare them with a sample of totally-eclipsing short-period W UMa systems from the literature.