Correlation between activity indicators: Hα and Ca II lines in M stars

BUCCINO, A P; IBAÑEZ BUSTOS, R.V.; MAUAS, P. J. D.

Congreso; Towards Future Research on Space Weather Drivers; 2019

Themagnetic fields responsible for the stellar activity are generated bythe stellar dynamo mechanism. Several late-type stars presentactivity cycles similar to the 11-year solar. Thestandard stellar activity indicator used is the Mount Wilson S-index,essentially the ratio of the Ca IIH&Kline-core fluxes to the continuum nearby. However,due to the low intrinsic luminosity of dMstarsthe S-index is not always suitablefor studying the chromospheric activity on thesefainterstars.Therefore,it is necessary to explore redder activityindicators inlate-type stars (eg.Balmer lines, Na lines or Ca IRT).Itis well known that the correlation between the the Ca IIand Haline-core fluxes is positive in the solar case for the wholesolar-cycle.However, during the last decade, this correlation has been revised forsolar-type stars.Themain conclusion is that this relationis not always valid for single stars.Since1999, the HKα Project is operating in the Argentinian observatoryCASLEO. Our group, systematically observe more than 150 main-sequencestars from F3 to M5.5. To date, we have more than 5000 mid-resolutionspectra, ranging from 389 to 669 nm, which constitute an idealdataset to study different chromospheric activity indicators atdifferent heights of the stellar atmosphere. Inthis work, wepresenta particularstudy of therelation between Haand Ca IIina set of 10southerndMe stars fordifferent level of activity.p { margin-bottom: 0.1in; line-height: 120%; }