Superflare G and K Stars and the Lithium abundance

TL;DR

This study investigates the relationship between superflares and lithium abundance in G and K stars, revealing correlations with stellar activity, rotation, and age, and identifying distinct groups with varying properties.

Contribution

It provides new insights into the connection between superflares, lithium content, and stellar activity, highlighting the diversity among superflare stars and their evolutionary states.

Findings

Superflare G and K stars are mainly fast-rotating young stars.

A subset of G stars with high lithium content are slow rotators with low activity.

Transition from saturation to solar-type activity occurs at specific rotation periods for different spectral types.

Abstract

We analyzed here the connection of superflares and the lithium abundance in G and K stars based on Li abundance determinations 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.