F-G-K stars activity indicators

In particular, the time-series of emissions in these two lines are clearly anti-correlated for a few percent of the stars, contrary to what is observed on the Sun. Our objective is to characterise these relationships in more detail using complementary criteria, and to constrain the properties of filaments and plages that are necessary to explain the observations.

We analysed the average level and variability of the H{alpha} and CaII emission for 441 F-G-K stars, paying particular attention to their (anti-)correlations on both short and long timescales. We also computed synthetic H{alpha} and CaII time-series for different assumptions of plage and filament properties and compared them with the observations. We were not able to find plage properties that, alone, are sufficient to reproduce the observations at all timescales simultaneously, even when allowing different H{alpha} and CaII emission relationships for different stars.