Photometry and H$alpha$ studies of a Low Mass Ratio Overcontact binary ASAS J082243+1927.0

TL;DR

This study combines photometric and H-alpha line observations to analyze a low mass ratio overcontact binary, revealing a potential merger scenario and a correlation between orbital period and H-alpha line strength.

Contribution

It provides the first detailed analysis of ASAS J082243+1927.0 using combined photometry and H-alpha studies, identifying a mass ratio cutoff near 0.085 and its implications for binary evolution.

Findings

The system has a mass ratio q = 0.106 and fill-out factor of 72%.

A correlation exists between orbital period and H-alpha equivalent width.

A mass ratio cutoff at q = 0.085 influences period evolution.

Abstract

Both high precision CCD photometric and H$alpha$ line studies are presented for an overcontact binary ASAS J082243+1927.0. The light curve exhibits a total eclipse at secondary minima along with an O'Connell effect. The light curve was modeled using the Wilson Devinney code and the best solution provides the mass ratio q = 0.106 and fill-out factor f = 72%. These parameters indicate that the system is a low mass ratio overcontact binary with a high degree of geometrical contact. The H alpha line equivalent width varied at different phases and it is found that the line is possibly filled-in at secondary minima. From a small sample of overcontact binaries, we found a correlation between the orbital period and H alpha line equivalent width of the primary component. Based on a sample of high filling factor and low mass ratio contact binaries, a mass ratio cut-off is observed at q = 0.085 in mass ratio - period plane. It was observed that below q $\le$ 0.085, period decreases with an increase in q and above it, period increases as the mass ratio increases. Interestingly, the observed mass ratio cut-off value lies close to the critical mass ratio range as predicted in the literature. The observational evidence of the cut-off of the mass ratio and its variation with orbital period are discussed in terms of mass transfer and angular momentum loss. Based on the results, we suggest that, ASAS J082243+1927.0 is at the verge of merger, eventually forming a fast rotating star.