Activity and the Li abundances in the FGK dwarfs

Aims. The aim of the present study is to determine the Li abundances for a large set of the FGK dwarfs and to analyse the connections between the Li content, stellar parameters, and activity. Methods. The atmospheric parameters, rotational velocities and the Li abundances were determined from a homogeneous collection of the echelle spectra with high resolution and a high signal-to-noise ratio. The rotational velocities v sini were determined by calibrating the cross-correlation function. The effective temperatures Teff were estimated by the line-depth ratio method. The surface gravities log g were computed by two methods: the iron ionization balance and the parallax. The LTE Li abundances were computed using synthetic spectra method. The behaviour of the Li abundance was examined in correlation with Teff ,[ Fe/ H], as well as withv sini and the level of activity in three stellar groups of the different temperature range. Results. The stellar parameters and the Li abundances are presented for 150 slow rotating stars of the lower part of the main sequence. The studied stars show a decline in the Li abundance with decreasing temperature Teff and a significant spread, which should be due to the difference of age of stars. The correlations between the Li abundances, rotational velocities v sini, and the level of the chromospheric activity were discovered for the stars with 6000 > Teff > 5700 K, and it is tighter for the stars with 5700 > Teff > 5200 K. The target stars with Teff < 5200 K do not show any correlation between logA(Li) and v sini. The relationship between the chromospheric and coronal fluxes in active with detected Li as well as in less active stars gives a hint that there exist different conditions in the action of the dynamo mechanism in those stars. Conclusions. We found that the Li-activity correlation is evident only in a restricted temperature range and the Li abundance spread seems to be present in a group of low chromospheric activity stars that also show a broad spread in the chromospheric vs. coronal activity.

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