Stellar activity of exoplanet hosts with STELLA
The characterization of exoplanets orbiting active stars can be severely limited by the presence of spots and faculae on the stellar surface. The photometric modulation caused by stellar activity can be detected and characterized using broad-band photometry in the visible over several rotation periods. I will present two cases in which the STELLA telescope provided a fundamental help on this regard: the discovery of the first multi-planet system in the open cluster M44 (Malavolta+2016), and the characterization of the cloudy atmosphere of GJ1214b (Nascimbeni+2015).