Photometric Analysis of Three Potential Red Nova Progenitors

TL;DR

This study analyzes three bright contact binary systems as potential red nova progenitors, highlighting their extreme low mass ratios, high magnetic activity, and instability, suggesting they may eventually merge.

Contribution

It provides detailed photometric analysis and magnetic activity assessment of three potential red nova progenitors, revealing their unstable configurations and high magnetic activity levels.

Findings

All three systems have extreme low mass ratios (0.075 to 0.097).

High magnetic activity indicated by UV excess and X-ray luminosity.

Systems are likely unstable and potential merger candidates.

Abstract

We present photometric analysis of three bright red nova progenitor contact binary systems: ASAS J082151-0612.6, TYC 7281-269-1 and TYC 7275-1968-1. The primary components in all three systems are solar-type low mass stars with radii somewhat larger than their Zero Age Main Sequence counterparts. The secondaries, as in most contact binary systems, have radii and luminosities well above their main sequence counterparts. All three have extreme low mass ratios ranging from 0.075 to 0.097 and two have high degrees of contact, in excess of 75%. All three have mass ratios and separations below the theoretical values for orbital stability. Chromospheric activity, a hallmark of magnetic activity and magnetic braking, considered important in mediating angular momentum loss, is also explored. All three systems demonstrate the O'Connell effect, and all systems require the introduction of star spots for a better light curve solution. In addition, we show that ASAS J082151-0612.6 and TYC 7281-269-1 have a UV colour excess in the range indicating high chromospheric activity. Another measure of potential significant magnetic activity is X-Ray luminosity; TYC 7275-1968-1, and probably also TYC 7281-269-1, have X-Ray luminosity well above other contact binary systems. We conclude that it is likely that all three are unstable and hence are potential merger candidates.