Cyclic activity in dM Stars

MAUAS, P. J. D.; BUCCINO, A. P.; PETRUCCI, R.; VIEYTES, M. C.; JOFRE, E.

Barcelona

Conferencia; 17th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun; 2012

ESA

During the last years, a new interest on M stars has emerged: due to their low masses, they are primary targets to search for terrestrial planets in the habitable zone. However, the activity signatures can hinder the detection of orbiting planets. Furthermore, the levels of UV radiation, which are strongly related to stellar activity, can also limit the habitability.  These facts make the analysis of activity in M stars relevant.Several late-type stars present activity cycles similar to the Solar one.  However, these cycles have been  mostly studied in F to K stars.  Due to their low intrinsic brightness, M stars are not usually the target of long-term observational studies of stellar activity, and therefore their long-term variability is generally not known.As a contribution on this subject, since 1999 we have developed an observing program at the Argentinian observatory Complejo Astronomico El Leoncito (CASLEO) dedicated to periodically obtain medium resolution echelle spectra of southern late-type stars. One of the main goals of our program was to extend the studies of stellar cycles to M- stars, at and beyond the limit for full convectivity.From our data, in previous works, we found an evidence of cyclic activity for the dMe 5.5 star Proxima Centauri, for the dMe 3.5 spectroscopic binary Gl 375 and, recently, for the M dwarfs: Gl 229 A (M1V) and Gl 752 A (M2.5V).In this poster we present a long-term study of near ten dM0 to dM5.5 stars. We also show the activity cycles detected in previous works and we further explore the one detected in Proxima Centauri by including last 5 years of data.