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NLTE model atmospheres for M dwarfs and giants

Published online by Cambridge University Press:  25 May 2016

Peter H. Hauschildt ,
France Allard ,
David R. Alexander ,
Andreas Schweitzer  and
E. Baron
Peter H. Hauschildt
Affiliation:
Dept. of Physics and Astronomy, Arizona State University, Box 871504, Tempe, AZ 85287-1504 E-Mail: yeti@sara.la.asu.edu
France Allard
Affiliation:
Dept. of Physics, Wichita State University, Wichita, KS 67260-0032
David R. Alexander
Affiliation:
Dept. of Physics, Wichita State University, Wichita, KS 67260-0032
Andreas Schweitzer
Affiliation:
Landessterwarte Heidelberg, Königstuhl, D-69117 Heidelberg
E. Baron
Affiliation:
Dept. of Physics and Astronomy, University of Oklahoma 440 W. Brooks, Rm 131, Norman, OK 73019-0225

Extract

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The atmospheres of M stars are dominated by a small number of very strong molecular compounds (H2O, TiO, H2, CO, VO). Most of the hydrogen is locked in molecular H2, most of the carbon in CO; and H2O, TiO and VO opacities define a pseudo-continuum covering the entire flux distribution of these stars. The optical “continuum” is due to TiO vibrational bands which are often used as temperature indicators for these stars. These may be the depth of the bands relative to the troughs in between them; or the depth of the VO bands; or of the atomic lines relative to the local “continuum”; or even the strength of the infrared water bands; all of these depend on the strength of the TiO bands and the amount of flux-redistribution to longer wavelengths exerted by them. Departures from LTE of the Ti I atom, and thus the concentration of the important TiO molecule, could, therefore, have severe and measurable consequences on the atmospheric structure and spectra of these stars.

Type
Session V: “Next Generation Model Atmospheres”
Information
Symposium - International Astronomical Union , Volume 176: Stellar Surface Structure , 1996 , pp. 539 - 546
Copyright
Copyright © Kluwer 1996 

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