Dr. Stefanie Rätz
Eberhard Karls Universität Tübingen

Abstract:

Stellar activity is directly linked to magnetic fields that are believed to be generated and maintained by a dynamo, which is driven by differential rotation and convection. Therefore, rotation and stellar activity are intimately connected. 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 provide rotation periods even with low amplitudes as well as a wealth of activity diagnostics.
We currently study the rotation-activity relation for a sample of ~9000 bright and nearby M dwarfs from the Superblink proper motion catalogue by Lepine and Gaidos (2011).
Our study of the rotation-activity relation based on photometric activity indicators from long cadence K2 data 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. Therefore, we have extended our work to K2 short cadence data to examine a possible influence of the data sampling on the shape of the rotation-activity relation, in particular with respect to the different sensitivity to the detection of stellar flares.
TESS observed 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 data cadence improves the detection and analysis of rotation and activity.

Veranstaltungslink/Kontakt: markus.mugrauer(at)uni-jena.de