Contributed Talk - Splinter Exoplanets

Thursday, 24 September 2020, 15:20   (virtual room D)

Flares and CMEs on cool stars

E.W. Guenther, P. Muheki, D. Wöckel
Thüringer Landessterwarte Tautenburg

It is now well established that the X-ray and extreme UV (XUV) radiation plays a crucial role in the evolution of a planet, in particular its atmosphere. While the impact of the XUV-radiation of the star is quiescence has already been studied in detail, the big unknown still are flares and Coronal-Mass Ejections (CMEs). The reason is that such studies would require very extended observing campaigns at XUV-wavelengths targeting young stars of different mass. We need to study young stars, because the first few 100 Myrs is the main activity phase in the life of a star. This is thus the phase at which the impact is largest. Another possibility is to use high-precision photometric data at optical wavelength. Such data is now available, thanks to the Kepler and TESS satellites. These missions provide us with superb statistics of flares but have the disadvantage that the data is not taken in the XUV-regime. However, using a reasonable assumption about the branching ratio between the XUV- and the optical-regime, the amount of XUV radiation that planets receive during their early life can be estimated. Spectroscopic observations of young stars provide us additionally with information on the ratio between CMEs and flares, and spectroscopic observations allow us to constrain the properties of the emitting region.