Photospheric activity, rotation, and star-planet interaction of the planet-hosting star CoRoT-6

TL;DR

This study models the photospheric activity and differential rotation of CoRoT-6, a star hosting a hot Jupiter, revealing potential star-planet magnetic interactions and quantifying stellar differential rotation.

Contribution

It presents a maximum entropy spot model of CoRoT-6's photospheric activity, estimating differential rotation and suggesting possible magnetic star-planet interactions.

Findings

Differential rotation lower limit of ΔΩ/Ω = 0.12 ± 0.02.

Active regions tend to lag the subplanetary point by about 200 degrees.

Photospheric activity may be influenced by magnetic star-planet interaction.

Abstract

The CoRoT satellite has recently discovered a hot Jupiter that transits across the disc of a F9V star called CoRoT-6 with a period of 8.886 days. We model the photospheric activity of the star and use the maps of the active regions to study stellar differential rotation and the star-planet interaction. We apply a maximum entropy spot model to fit the optical modulation as observed by CoRoT during a uninterrupted interval of about 140 days. Photospheric active regions are assumed to consist of spots and faculae in a fixed proportion with solar-like contrasts. Individual active regions have lifetimes up to 30-40 days. Most of them form and decay within five active longitudes whose different migration rates are attributed to the stellar differential rotation for which a lower limit of \Delta \Omega / \Omega = 0.12 \pm 0.02 is obtained. Several active regions show a maximum of activity at a longitude lagging the subplanetary point by about 200 degrees with the probability of a chance occurrence being smaller than 1 percent. Our spot modelling indicates that the photospheric activity of CoRoT-6 could be partially modulated by some kind of star-planet magnetic interaction, while an interaction related to tides is highly unlikely because of the weakness of the tidal force.