Cyclic activity in dM Stars

PABLO MAUAS; ADREA BUCCINO; ROMINA PETRUCCI; MARIELA VIEYTES; EMILIANO JOFRÉ

Barcelona

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

Institut d'Estudis Espacials de Catalunya (IEEC), Consejo Superior de Investigaciones Científicas (CSIC) and Institut de Ciències de l'Espai (ICE).

Due to their low masses, dM stars are primary targets to search for terrestrialplanets. However, they tend to be more active than earlier type stars, a fact whichcan 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 factsmake the analysis of activity in M stars relevant.The usually accepted model to describe the generation and intensification ofmagnetic fields in late F- to early M-type stars is the  aw-dynamo, first invoked toexplain solar activity. In this model the large-scale magnetic field generation resultsfrom the interaction of differential rotation in the tachocline and the convectiveturbulence. Since stars with spectral type later than M3 are believed to be fullyconvective, they should not be able to sustain a solar-like dynamo.To date, activity cycles have been detected in several late-type stars. However,these works are mainly concentrated on F to K stars, since due to the long exposuretimes needed to observe them, the red and faint M dwarfs are usually not the targetof long-term observational studies of stellar activity. As a contribution to this subject,we have developed an observing program dedicated to periodically obtain mediumresolution echelle spectra of southern late-type stars, including those stars which arefully-convective. In this work, we summarized our main results on cyclic activity of dMstars.