Investigating stellar activity with CoRoT data and complementary ground-based observations

TL;DR

This paper demonstrates the first detection of stellar magnetic activity variations using asteroseismic data from CoRoT, complemented by ground-based observations, revealing activity-related frequency shifts similar to solar behavior.

Contribution

It presents the first analysis of stellar activity variations through asteroseismic data, showing correlations with surface activity and extending solar activity studies to other stars.

Findings

Detected magnetic activity variability in HD49933 using asteroseismology.

Observed frequency shifts correlated with activity levels, similar to solar patterns.

Confirmed surface activity variations with Ca H&K monitoring, showing >20% activity change.

Abstract

Recently, the study of the CoRoT target, HD49933, showed evidence of variability of its magnetic activity. This was the first time that a stellar activity was detected using asteroseismic data. For the Sun and HD49933, we observe an increase of the p-mode frequencies and a decrease of the maximum amplitude per radial mode when the activity level is higher. Moreover, we have been able to determine the variation of the frequency shift as a function of frequency, a premier in a star different from the Sun, showing pretty interesting similarities with the behavior already seen in the Sun. Beside, surface activity is now confirmed by the continuous monitoring done in Ca H&K during 6 months last fall. The peak-to-peak activity level seems to be bigger than 20% (close to the solar level, which is around 25%). We studied some other CoRoT solar-like targets as well for which modes have been detected and well identified, e.g. HD181420 and HD52265 (which is hosting a planet). Although HD52265 rotates much slower than HD49933 meaning much longer activity cycle (compared to the CoRoT observations), we do indeed see a hint of an increase in the activity level of that star...