Abstract
Aims. The aim of this paper is to provide fundamental parameters and abundances with a high accuracy for a large sample of cool main sequence stars. This study is part of wider project, in which the metallicity distribution of the local thin disc is investigated from a complete sample of G and K dwarfs within 25 pc. Methods. The stars were observed at high resolution and a high signal-to-noise ratio with the ELODIE echelle spectrograph. The V sini were obtained with a calibration of the cross-correlation function. Effective temperatures were estimated by the line depth ratio method. Surface gravities (log g) were determined by two methods: parallaxes and ionization balance of iron. The Mg and Na abundances were derived using a non-LTE approximation. Abundances of other elements were obtained by measuring equivalent widths. Results. Rotational velocities, atmospheric parameters (Teff ,l ogg ,[ Fe/H], Vt ), and Li, O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Co, Ni, and Zn abundances are provided for 131 stars. Among them, more than 30 stars are active stars with a fraction of BY Dra and RS CVn type stars for which spectral peculiarities were investigated. We find the mean abundances of the majority of elements in active and nonactive stars to be similar, except for Li, and possibly for Zn and Co. The lithium is reliably detected in 54% of active stars but only in 20% of nonactive stars. No correlation is found between Li abundances and rotational velocities. A possible anticorrelation of log A(Li) with the index of chromospheric activity GrandS is observed. Conclusions. Active and nonactive cool dwarfs show similar dependencies of most elemental ratios vs. [Fe/H]. This allows us to use such abundance ratios to study the chemical and dynamical evolution of the Galaxy. Among active stars, no clear correlation has been found between different indicators of activity for our sample stars.
Highlights
With this new contribution, we continue our effort to determine homogeneous atmospheric parameters and abundances for large samples of stars, dwarfs, and giants (Mishenina et al 2004, 2006), in order to investigate the chemical and dynamical evolution of the Galactic disc
Based on spectra collected with the ELODIE spectrograph at the 1.93-m telescope of the Observatoire de Haute Provence (France)
The spectra of 131 stars were obtained using the 1.93 m telescope at Observatoire de Haute-Provence (OHP, France) equipped with the échelle-spectrograph ELODIE which gives a resolving power of R = 42 000
Summary
We continue our effort to determine homogeneous atmospheric parameters and abundances for large samples of stars, dwarfs, and giants (Mishenina et al 2004, 2006), in order to investigate the chemical and dynamical evolution of the Galactic disc. Following this approach, in which kinematical and chemical information is combined, long-lived G and K dwarfs within 25 pc from the Sun were selected in the Hipparcos catalogue in order to investigate the metallicity distribution in the Solar Neighbourhood from an unbiased sample and with accurate spectroscopic metallicities. The sample of G and K dwarfs presented here gave us an unique opportunity to analyse the spectral features and chemical composition of these active stars in comparison to less active dwarfs This is of particular interest because the Sun is suspected of belonging to the BY Dra type. Mishenina et al.: Spectroscopic investigation of stars on the lower main sequence various properties upon star rotation (v sin i) and chromospheric activity; 3) the general behaviour of various element’s abundances with metallicity [Fe/H] of active and nonactive stars; and 4) the lithium abundance as an indicator of chromospheric activity
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
