A Study of Six Extreme Low Mass Ratio Contact Binary Systems

TL;DR

This study analyzes six extreme low mass ratio contact binary systems using multi-band photometric and spectroscopic data, revealing their magnetic activity, period variations, and potential for future merger.

Contribution

It provides detailed analysis of six contact binaries with extremely low mass ratios, including their magnetic activity, period changes, and stability assessments, which is novel for such systems.

Findings

All six systems have extreme low mass ratios (0.073 to 0.149).

Five of six systems show ultraviolet excess indicating magnetic activity.

Three systems are potential merger candidates based on stability analysis.

Abstract

Multi-band (B, V and R) photometric and spectroscopic observations of six poorly studied contact binaries carried out at the Western Sydney University and Las Cumbres Observatory were analysed using a recent version of the Wilson-Devenney code. All six were found to be of extreme low mass ratio ranging from 0.073 to 0.149. All are of F spectral class with the mass of the primary component ranging from 1.05Msun to 1.48Msun. None show light curve features of enhanced choromospheric activity (O'Connell Effect) however five of the six do have significant ultraviolet excess indicating presence of increased magnetic and chromospheric activity. Period analysis based on available survey data suggests two systems have a slowly increasing period suggesting mass transfer from the secondary to the primary, two have a slow declining period with likely mass transfer from primary to the secondary while one shows a steady period and one undergoing transition from a declining to increasing period suggesting possible mass transfer reversal. We also compare light curve solutions against theoretical markers of orbital stability and show that three of six systems have mass ratios within the theoretical instability limit and maybe regarded as potential merger candidates.