Journal Article

Metallicity and photospheric abundances in field K and M dwarfs

M. Zboril and P. B. Byrne

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 299, issue 3, pages 753-758
Published in print September 1998 | ISSN: 0035-8711
Published online September 1998 | e-ISSN: 1365-2966 | DOI:
Metallicity and photospheric abundances in field K and M dwarfs

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Elemental abundances in late-type stars are of interest in several ways: they determine the location of the stars in the HR diagram and therefore their ages, as well as the atmospheric structure in their middle and upper photospheres. Especially in the case of chromospherically active late-type stars the question arises to what degree the upper photosphere is influenced by the nearby chromosphere. Analysing S/N ∼ 200 and Δλ/λ ∼ 20 000 data, we found a mean metallicity index [M/H] = −0.2 for programme K and M field stars based on an analysis of spectra in the region 5500–9000 Å. We also found that the Ca i 6162-Å transition is a potential surface gravity indicator for K-type stars. For the chromospheric activity interval 4.4 < log FMgii < 6.6 we did not find any chromospheric activity impact on photospheric and upper photospheric transitions. With the derived metallicity, we confirmed the Li abundance from our previous paper and thus its dependence on the Mg ii chromospheric activity index. The nature of the spectrum for the active M-type star Gl 896A is explained by pure rotation of 14 km s−1. As far as the lithium—rotation relation is concerned, the spectrum of Gl 517 is rotationally broadened as well, by 12 km s−1, and the Li abundance is the second highest in our sample of stars. However, there is no link between very high Li abundance, 2.2 dex, in the K dwarf star Gl 5 and stellar rotation.

Keywords: stars: abundances; stars: activity; stars: chromospheres; stars: fundamental parameters; stars: late-type

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Subjects: Astronomy and Astrophysics

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