A possible activity cycle in Proxima Centauri

CINCUNEGUI, C. C.; DÍAZ, R. F.; MAUAS, P.J.D.

ASTRONOMY AND ASTROPHYSICS

EDP

Lugar: Paris; Año: 2007 vol. 461 p. 1107 - 1113

0004-6361

Context: Several late-type stars present activity cycles resembling the Solar one. This fact has been observed mostly in stars ranging from F to K, i.e., in stars with a radiative core and an outer convective layer. Aims: This work aims at studying whether an activity cycle can be detected in the dM5.5e star Proxima Centauri, which is supposed to be completely convective. Methods: We present periodical medium-resolution echelle observations covering the complete visual range, which were taken at the CASLEO Argentinean Observatory. These observations are distributed over 7 years. We discarded the spectra that present flare activity, and analyze the remaining activity levels using four different statistical techniques to look for a period of activity. Results: We find strong evidence of a cyclic activity, with a period of ~442 days. We also estimate that the Ca ~II S index varies around 130% due to activity variations outside of flares.