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Unveiling stellar magnetic activity using CoRoT seismic observations
|High Altitude Observatory|
|Low degree solar and stellar seismology|
|Auteur(s) supplémentaire(s)||R.A Garcia, D. Salabert, J. Ballot, C. Regulo, T.S. Metcalfe, A. Baglin|
|Institution(s) supplémentaire(s)||CEA Saclay, IAC, Universidad de la Laguna, LATT, Observatoire de Meudon|
|It is well known that in the Sun, the frequencies and amplitudes of acoustic modes vary throughout the solar cycle. Indeed, while the magnetic activity goes towards its maximum, the frequencies of the modes increase and their amplitudes decrease.|
We have analyzed data from the CoRoT mission on a few stars that exhibit solar-like oscillations. The study of HD49933 (observed during 60 days and 137 days spanning a total of 400 days) showed a modulation of the maximum amplitude per radial mode and the frequency shifts of the modes, showing magnetic activity in this rapidly rotating star. Moreover, both properties vary in an anticorrelated way and the data allowed us to establish a lower limit for the cycle period of ~120 days. Preliminary measurements in Ca H and K lines showed that this star is in the "active stars" category.
We will also discuss the results obtained for other targets such as HD181420 and HD49835 for which we have investigated a similar behavior.