The 19th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun Edited by G. A. Feiden Superflare G and K Stars and the Lithium abundance Maria M. Katsova,1 Moisey A. Livshits,2 Tamara V. Mishenina,3 Bulat A. Nizamov4 1 Sternberg State Astronomical Institute, Lomonosov Moscow State University, Moscow, Russia 2 Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation of Russian Academy of Sciences, Troitsk, Russia 3 Astronomical Observatory, Odessa National University, Odessa, Ukraine 4 Department of Physics, Lomonosov Moscow State University, Moscow, Russia Abstract We analyzed here the connection of superflares and the lithium abundance in G and K stars based on Li abundance determi- nations conducted with the echelle spectra of a full set of 280 stars obtained with the ELODIE spectrograph. For high-active stars we show a definite correlation between log A(Li) and the chromosphere activity. We show that sets of stars with high Li abundance and having superflares possess common properties. It relates, firstly, to stars with activity saturation. We consider the X-ray data for G, K, and M stars separately, and show that transition from a saturation mode to solar-type activity takes place at values of rotation periods 1.1, 3.3, and 7.2 days for G2, K4 and M3 spectral types, respectively. We discuss bimodal distribution of a number of G and K main-sequence stars versus an axial rotation and location of superflare stars with respect to other Kepler stars. We conclude that superflare G and K stars are mainly fast rotating young objects, but some of them belong to stars with solar-type activity. At the same time, we found a group of G stars with high Li content (log A(Li) = 1.5 −3), but being slower rotators with rotation periods > 10 days, which are characterized by low chromospheric activity. This agrees with a large spread in Li abundances in superflare stars. A mechanism leading to this effect is discussed. Keywords: Stars: activity – Stars: coronae – Stars: rotation – Stars: flares – Stars: abundances 1 Introduction One of the most important results of study of activity of low-mass stars is a detection with the Kepler mission of su- perflares whose total energy in optics and near IR-range is 1033 −1035 ergs, that is by 2–4 orders of magnitudes more than the total energy of the largest flares on the Sun. What distinguishes the stars where such cataclisms can occur? This problem is solved in two ways; first is determination of fundamental parameters and flare occurrence frequencies. This was fulfilled by Maehara et al. (2012) and Notsu et al. (2015a, b) where they found that these events are typical for G and partly K stars, which rotate faster than field stars and are more magnetically active. Another way is comparison of general properties of superflare stars with distinctive fea- tures of other kinds of active late-type stars. This is com- parison of activity at different layers of stellar atmospheres. Messina et al. (2003) were the first who have analyzed rota- tional modulation of the optical continuum caused by spots and the X-ray fluxes of stars of different spectral types. Lately new X-ray data and observations of optical variability of many late-type stars with the Kepler misson have appeared. Recently we considered a possibility of occurrence of very powerful events on late-type stars in the frameworks of cur- rent ideas on solar flares (Katsova and Livshits, 2015). Wich- mann et al. (2014) Şstarted a programme to study the nature of the stars on which these super flares have been observed.Ť Here we are trying to analyze features of those stars, where such extremal phenomena occur, on the base of new results of multiwavelength observations of late-type stars. 2 Where do Superflares Occur? As an example, let us consider a restricted set of Kepler’s stars where superflare light curves were registered with the higher temporal resolution (1 min). We use data for 83 active late-type dwarfs fro