Kepler super-flare stars: what are they?

The Kepler mission has led to the serendipitous discovery of a significant number of “super flares” – white light flares with energies between 1033 erg and 1036 erg – on solar-type stars. It has been speculated that these could be “freak” events that might happen on the Sun, too. We have started a programme to study the nature of the stars on which these super flares have been observed. Here we present high-resolution spectroscopy of 11 of these stars and discuss our results. We find that several of these stars are very young, fast-rotating stars where high levels of stellar activity can be expected, but for some other stars we do not find a straightforward explanation for the occurrence of super flares.