BSN-II: The First Light Curve Study of Eight Total Eclipsing Contact Binary Stars with Shallow Fillout Factors

TL;DR

This paper presents the first detailed light curve analysis of eight total-eclipse contact binary stars with shallow fillout factors, revealing period changes, stellar parameters, and evolutionary insights using photometric data and Gaia parallaxes.

Contribution

It provides the first comprehensive light curve study of these binaries, including period analysis, spot modeling, and stellar parameter estimation with Gaia data.

Findings

Four binaries show increasing orbital periods.

Two binaries require starspot modeling.

All systems have shallow fillout factors.

Abstract

This study provides the first comprehensive analysis of eight total-eclipse W Ursae Majoris-type contact binary systems. Ground-based photometric multiband observations were conducted at a Mexican observatory, and new times of minima were extracted. The O-C analysis reveals that four of our target binaries exhibit a long-term increase in their orbital periods, while the others show a long-term decrease in their orbital periods. We analyzed the light curves using the PHOEBE Python code and BSN application. Among the target systems, two required the inclusion of a cold starspot on one of the components to achieve an adequate fit. The light curve analysis revealed that the target systems exhibit a shallow fillout factor. Absolute parameters were estimated using the Gaia DR3 parallax and astrophysics equations. Considering the effective temperatures and component masses, each system was classified as either the A- or W-subtype. The stellar evolution of the systems was represented through the mass-radius and mass-luminosity diagrams. Additionally, we calculated the initial masses of the companion stars and the total mass lost for each target system.