title: CoRoT reveals a magnetic activity cycle in a Sun-like star.
abstract: The 11-year activity cycle of the Sun is a consequence of a dynamo process occurring beneath its surface. We analyzed photometric data obtained by the CoRoT space mission, showing solarlike oscillations in the star HD49933, for signatures of stellar magnetic activity. Asteroseismic measurements of global changes in the oscillation frequencies and mode amplitudes reveal a modulation of at least 120 days, with the minimum frequency shift corresponding to maximum amplitude as in the Sun. These observations are evidence of a stellar magnetic activity cycle taking place beneath the surface of HD49933 and provide constraints for stellar dynamo models under conditions different from those of the Sun.
authors.affiliation: Laboratoire Astrophysique, Instrumentation, et Modélisation, CEA/Direction des Sciences de la Matière-CNRS, Université Paris 7 Diderot, Institut de Recherche sur les Lois Fondamentales de l'Univers/Service d'Astrophysique, Centre de Saclay, 91191 Gif-sur-Yvette, France. Rafael.Garcia@cea.fr
authors.forename: Rafael A
authors.initials: RA
authors.lastname: García
authors.forename: Savita
authors.initials: S
authors.lastname: Mathur
authors.forename: David
authors.initials: D
authors.lastname: Salabert
authors.forename: Jérôme
authors.initials: J
authors.lastname: Ballot
authors.forename: Clara
authors.initials: C
authors.lastname: Régulo
authors.forename: Travis S
authors.initials: TS
authors.lastname: Metcalfe
authors.forename: Annie
authors.initials: A
authors.lastname: Baglin