Volume 542, June 2012
|Number of page(s)||14|
|Published online||21 June 2012|
1 Department of Physics and Astronomy, Uppsala University, Box 516, S-751 20 Uppsala, Sweden
2 Laboratoire Univers et Particules de Montpellier, CNRS, Université Montpellier 2, 34095 Montpellier, France
3 Universität Göttingen, Institut für Astrophysik, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
Received: 15 September 2011
Accepted: 30 November 2011
Context. The relatively wide spread in the derived metallicities ([Fe/H]) of M dwarfs shows that various approaches have not yet converged to consistency. The presence of strong molecular features and incomplete line lists for the corresponding molecules have made determining the metallicity of M dwarfs difficult. Furthermore, the faint M dwarfs require long exposure times for the signal-to-noise ratio needed for a detailed spectroscopic abundance analysis.
Aims. We present a high-resolution (R ~ 50 000) spectroscopic study of a sample of eight single M dwarfs and three wide-binary systems observed in the infrared J band.
Methods. The absence of large molecular contributions allows for a precise continuum placement. We derived metallicities based on the best fit of synthetic spectra to the observed spectra. To verify the accuracy of the applied atmospheric models and test our synthetic spectrum approach, three binary systems with a K-dwarf primary and an M-dwarf companion were observed and analysed along with the single M dwarfs.
Results. We obtain good agreement between the metallicities derived for the primaries and secondaries of our test binaries, thereby confirming the reliability of our method of analysing M dwarfs. Our metallicities agree well with some earlier determinations, and deviate from others.
Conclusions. We conclude that spectroscopic abundance analysis in the J band is a reliable method for establishing the metallicity scale for M dwarfs. We recommend its application to a larger sample covering lower, as well as higher, metallicities. Further prospects for the method include abundance determinations for individual elements.
Key words: stars: abundances / techniques: spectroscopic / stars: atmospheres / stars: low-mass / binaries: visual
Based on data obtained at ESO-VLT, Paranal Observatory, Chile, Program ID 082.D-0838(A) and 084.D-1042(A).
Table 2 is available in electronic form at http://www.aanda.org
Electronic version of the spectra is only available at CDS via anonymous ftp to cdsarc.u-strasbg.fr (184.108.40.206) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/542/A33
© ESO, 2012
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