Modelling of an eclipsing RS CVn-binary: V405 And

TL;DR

This paper models the eclipsing binary V405 And, revealing that magnetic activity influences stellar radii, with the primary star showing an unusually large radius likely due to magnetic effects.

Contribution

It provides detailed light curve modeling of V405 And, demonstrating the impact of magnetic activity on stellar structure, especially the primary star's inflated radius.

Findings

Primary star's radius exceeds theoretical predictions for inactive stars.

Light curve changes indicate significant magnetic activity and star spots.

Supports the theory that magnetic activity affects stellar radii.

Abstract

V405 And is an ultrafast-rotating (P_rot ~ 0.46 days) eclipsing binary. The system consists of a primary star with radiative core and convective envelope, and a fully convective secondary. Theories have shown, that stellar structure can depend on magnetic activity, i.e., magnetically active M-dwarfs should have larger radii. Earlier light curve modelling of V405 And indeed showed this behaviour: we found that the radius of the primary is significantly larger than the theoretically predicted value for inactive main sequence stars (the discrepancy is the largest of all known objects), while the secondary fits well to the mass-radius relation. By modelling our recently obtained light curves, which show significant changes of the spotted surface of the primary, we can find further proof for this phenomenon.