Spectroscopic characterization of superflares on solar-type stars - a joint observing campaign

During the last decade numerous superflares have been detected on solar-type stars using broadband photometry from the Kepler and TESS satellites. Still the spectroscopic exploration of this high-energy phenomenon is lacking. This exploration would reveal what makes normal flares different from superflares. The spectroscopic detection of superdlares requires dedicated observational efforts, as this phenomenon is sporadic. We present here one step of joint observational efforts to spectroscopically characterize superflares. We focus on the solar-type stars EK Dra, V833 Tau, and BY Dra, as those are relatively bright and active, and especially V833 Tau shows a high superflare rate in TESS data. The spectroscopic observations have been done at the Skalnate Pleso observatory operated by the Slovak Academy of Sciences and the Ondrejov observatory operated by the Czech Academy of Sciences. Coordinated photometry in two filters has been done at Stara Lesna/Skalnate Pleso observatory run by the Slovak Academy of Sciences, ELTE Gothard Astrophysical Observatory, Szombathely, Hungary, and Lustbuhel Observatory run by the University of Graz, Austria. In total around 24 hours were spent on EK Dra, 12 hours on BY Dra, and 20 hours on V833 Tau. However, no superflares have been detected. We discuss detection probabilities and the importance of studying superflares spectroscopically.