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The study of stellar activity is important because it can provide new constraints for dynamo models, when combined with surface rotation rates and the depth of the convection zone. We know that the dynamo mechanism, which is believed to be the main process to rule the magnetic cycle of solar-like stars at least, results from the interaction between (differential) rotation, convection, and magnetic field. The Kepler mission has been collecting data for a large number of stars during 4 years allowing us to investigate magnetic stellar cycles. We investigated the Kepler light curves to look for magnetic activity or even hints of magnetic activity cycles. Based on the photometric data we also looked for new magnetic indexes to characterise the magnetic activity of the stars. We selected a sample of 22 solar-like F stars that have a rotation period smaller than 12 days. We performed a time-frequency analysis using the Morlet wavelet yielding a magnetic proxy. We computed the magnetic index S_ph as the standard deviation of the whole time series and the index <S_ph> that is the mean of standard deviations measured in subseries of length five times the rotation period of the star. We defined new indicators to take into account the fact that complete magnetic cycles are not observed for all the stars, such as the contrast between high and low activity. We also inferred the Rossby number of the stars and studied their stellar background. This analysis shows different types of behaviours in the 22 F stars. Two stars show behaviours very similar to magnetic activity cycles. Five stars show long-lived spots or active regions suggesting the existence of active longitudes. Two stars of our sample seem to have a decreasing or increasing trend in the temporal variation of the magnetic proxies. Finally the last group of stars show magnetic activity (with presence of spots) but no sign of cycle.
The properties of the acoustic modes are sensitive to magnetic activity. The unprecedented long-term Kepler photometry, thus, allows stellar magnetic cycles to be studied through asteroseismology. We search for signatures of magnetic cycles in the se
In the Sun, the frequencies of the acoustic modes are observed to vary in phase with the magnetic activity level. These frequency variations are expected to be common in solar-type stars and contain information about the activity-related changes that
Monitoring chromospheric and photospheric indexes of magnetic activity can provide valuable information, especially the interaction between different parts of the atmosphere and their response to magnetic fields. We extract chromospheric indexes, S a
Asteroseismology of F-type stars has been hindered by an ambiguity in identification of their oscillation modes. The regular mode pattern that makes this task trivial in cooler stars is masked by increased linewidths. The absolute mode frequencies, e
Mapping lithium evolution for evolved stars will provide restrictions and constraints on the fundamental stellar interior physical processes, which further shed light on our understanding of the theory of stellar structure and evolution. Based on a s