Chromospheric activity in Proxima Centauri

CINCUNEGUI, C.; MAUAS, P.J.D.

Hamburgo, Alemania.

Workshop; 13th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun; 2004

European Space Agency

In this work we present Echelle spectra of the dM5.5eflare star Proxima Centauri, obtained in the CASLEO observatory.We have 44 observations from 1999 to date,taken in 11 different observing runs, which were flux calibrated.The index mostly used to measure stellar activity isthe one combining Ca II H&K line fluxes. These lines,which are formed in the stellar chromosphere, are not particularlyadequate to study cool stars, which are intrinsicallyfaint and red. We construct an index from Hα, whichshows a good correlation with the Ca II lines and is moresuitable for this cool star, due to its longer wavelength.We found that the He I D3 line can be a useful proxy todiscriminate the average chromospheric activity from thefrequent flaring activity. We could separate this transientactivity using this index, and we found that the remainingvariability is compatible with the existence of an activitycycle of around 1300 days as suggested in previous works.