The importance of studying active giant stars in eclipsing binaries -- and the role of citizen scientists in finding them

Abstract

Red giant stars with deep convection zones and rapid rotation maintain a strong surface magnetic field which may alter their observable astrophysical parameters. The resulting lower surface temperature due to spots makes the inferred masses and ages from evolutionary tracks uncertain. Eclipsing binaries having an active giant component can help in finding the stellar mass independently. However, until the recent space missions it was nearly impossible to find such systems from the ground. Since the evolution on the giant branch is rapid, the number of binaries containing giant stars is low. The eclipses, if the inclination allows, are very shallow, on the order of the photometric accuracy from the ground, due to the large brightness difference between a red giant primary and its solar size or smaller secondary. And, the typically acquired data from the ground are not uniform or continuous. In this paper, a few new eclipsing binaries are presented with active giant components observed by TESS and discovered by citizen scientists, which are worthy of further studies.