Lithium abundance of the solar-type superflare stars
Satoshi Honda

We will present the Lithium abundances in the solar-type superflare stars to investigate the nature of such stars and the differences of the Sun. Young stars, close binary stars, and dMe stars sometimes produce “superflares”, flares whose total energy is 10-10^6 times larger than the largest flares on the Sun. It has been recognized that the superflares will not occur on the slowly rotating, single solar-type stars (Sun-like stars). However, Maehara et al. (2012) and Shibayama et al. (2013) found the superflare events on Sun-like stars from the photometric data of Kepler spacecraft. We performed the high dispersion spectroscopy of solar-type superflare stars by Subaru/HDS, and estimate the stellar parameters and lithium abundance of the stars to compare with the Sun. Our spectroscopic analysis of superflare stars show more than half of targets have no evidence of binary system and the stellar parameters are in the range of solar-type stars (Notsu et al. 2015a&b). We also investigate the correlations of Lithium abundance with stellar atmospheric parameters, rotational velocity, and superflare activities to understand the nature of superflare stars and the possibility of the nucleosynthesis of lithium by superflares. The derived lithium abundance in superflare stars do not show the correlation with stellar parameters. As compared with the lithium abundance in Hyades cluster which is younger than the sun, it is suggested that half of observed stars are young. However, there are some objects which show the low lithium and slowly rotate from the estimated vsini and period of brightness variation. This results indicates that the superflare stars are not only young stars but also old stars like our sun. In our observations, we could not find the any evidence of lithium productions by superflare.