Long-term chromospheric activity in southern M dwarfs: Gl 229 A and Gl 752 A

TL;DR

This study investigates the long-term chromospheric activity cycles of two southern M dwarf stars, Gl 229 A and Gl 752 A, revealing potential activity periods of approximately 4 and 7 years through spectroscopic and photometric analysis.

Contribution

First long-term observational analysis of activity cycles in M dwarfs using spectroscopic and photometric data, identifying possible periodicities.

Findings

Detected ~4-year activity cycle in Gl 229 A.

Detected ~7-year activity cycle in Gl 752 A.

Demonstrated feasibility of long-term activity monitoring in M dwarfs.

Abstract

Several late-type stars present activity cycles similar to that of the Sun. However, these cycles have been mostly studied in F to K stars. Due to their small intrinsic brightness, M dwarfs are not usually the targets of long-term observational studies of stellar activity, and their long-term variability is generally not known. In this work, we study the long-term activity of two M dwarf stars: Gl 229 A (M1/2) and Gl 752 A (M2.5). We employ medium resolution echelle spectra obtained at the 2.15 m telescope at the Argentinian observatory CASLEO between the years 2000 and 2010 and photometric observations obtained from the ASAS database. We analyzed Ca \II K line-core fluxes and the mean V magnitude with the Lomb-Scargle periodogram, and we obtain possible activity cycles of $\sim$4 yr and $\sim$7 yr for Gl 229 A and Gl 752 A respectively.