Talk

The rotation-activity relation of M dwarfs: From K2 to TESS and PLATO

Stefanie Raetz, Institute for Astronomy and Astrophysics (IAAT) Tuebingen

Studies of the rotation-activity relation of late-type stars are essential to enhance our understanding of stellar dynamos and angular momentum evolution. Photometric observations with space telescopes such as the K2 and TESS missions provide rotation periods even with low amplitudes as well as a wealth of activity diagnostics. We currently study the rotation-activity relation with K2 for M dwarfs where it is especially poorly understood. Our study is based on the Superblink proper motion catalogue of ~9000 bright and nearby M dwarfs by Lepine and Gaidos (2011).The rotation-activity relation based on photometric activity indicators revealed, that, at a critical rotation period of ~10d, the activity level changes abruptly. This phenomenon represents an open problem within the framework of dynamo theory. Despite the outstanding capabilities of K2, the short observational baseline and the low cadence allows us to detect only short rotation periods and long duration flares which represents a strong bias for such activity studies. TESS observes in its two years main mission almost all bright M-dwarfs from the Superblink catalogue. Although TESS observes one sector for only ~27d, it will provide up to thirteen 27d-light curves for ~2% of the targets due to the overlap of the sectors. TESS drastically enlarges our sample of continuous high cadence monitored bright M-dwarfs and allows us to study in depth the activity and in particular the morphology of flares. In the future, the PLATO mission with its unprecedented precision, short cadence and long observational baseline, allows us to study the magnetic activity indicators in up to now unrivaled detail. In my talk I will explain the results of our K2 study and show the application of the activity analysis methods to TESS data. Furthermore, I will describe how a higher cadence and a longer duration improves the determination of rotation periods and the detection of stellar flares.