Chromospheric Long Term Activity of Very Cool Stars

MAUAS, P.J.D.; BUCCINO, A.P.

Puerto Vallarta

Congreso; New Quests in Stellar Astrophysics III: A Panchromatic View of Solar-like Stars, With and Without Planets; 2013

We study the long-term chromospheric activity of dM stars, using in particularthe results of an observational program we started in 1999, to systematically obtainmid-resolution spectra of late-type stars. First, we discuss which are good activityindicators for these stars. We investigated the relation between the activity measurementsin the calcium and hydrogen lines, and found that the usual correlation observedreflects differences between stars, and it is not always preserved for simultaneous observationsof a particular star. Later we investigate the variations in individual stars, andwe report cyclic activity in four dM stars, including Prox-Cen.