A&A 439, 1137-1148 (2005)
PHOENIX model chromospheres of mid- to late-type M dwarfsB. Fuhrmeister, J. H. M. M. Schmitt and P. H. Hauschildt
Hamburger Sternwarte, University of Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
(Received 9 November 2004 / Accepted 28 April 2005)
We present semi-empirical model chromospheres computed with the atmosphere code PHOENIX. The models are designed to fit the observed spectra of five mid- to late-type M dwarfs. Next to hydrogen lines from the Balmer series we used various metal lines, e.g. from Fe I, for the comparison between data and models. Our computations show that an NLTE treatment of C, N, O impacts on the hydrogen line formation, while NLTE treatment of less abundant metals such as nickel influences the lines of the considered species itself. For our coolest models we investigated also the influence of dust on the chromospheres and found that dust increases the emission line flux.
Key words: stars: activity -- stars: late-type -- stars: chromospheres
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