12 Years of Stellar Activity Observations in Argentina

TL;DR

This paper reports 12 years of systematic spectroscopic observations of late-type stars in Argentina, revealing cyclic activity, calibrating activity indices, and modeling stellar chromospheres to understand stellar magnetic activity.

Contribution

It provides a long-term observational dataset, new calibration of activity indices, and insights into chromospheric activity trends across spectral types.

Findings

Detected cyclic activity in four dM stars, including Prox-Cen.

Calibrated the S index to flux conversion over a wider spectral range.

Found a consistent trend in chromospheric radiative losses for G and K dwarfs.

Abstract

We present an observational program we started in 1999, to systematically obtain mid-resolution spectra of late-type stars, to study in particular chromospheric activity. In particular, we found cyclic activity in four dM stars, including Prox-Cen. We directly derived the conversion factor that translates the known S index to flux in the Ca II cores, and extend its calibration to a wider spectral range. We investigated the relation between the activity measurements in the calcium and hydrogen lines, and found that the usual correlation observed is the product of the dependence of each flux on stellar color, and it is not always preserved when simultaneous observations of a particular star are considered. We also used our observations to model the chromospheres of stars of different spectral types and activity levels, and found that the integrated chromospheric radiative losses, normalized to the surface luminosity, show a unique trend for G and K dwarfs when plotted against the S index.