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Molecular Opacities in Cool Dwarf Stars

Published online by Cambridge University Press:  12 April 2016

James Liebert
James Liebert*
Affiliation:
Steward Observatory, University of Arizona, Tucson AZ 85721, USA

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The term dwarf stars identifies objects of small radius in the Hertzsprung-Russell (H-R) Diagram, but encompasses more than one phase of stellar evolution. The M dwarfs (type dM) populate the main sequence at the low mass end; these are the coolest core hydrogen-burning stars. They belong generally to the Galactic disk, or Population I, have relatively small space motions with respect to the Sun, and have similar metallicities to the Sun (although perhaps only within a factor of several). In particular, this means that the abundance of oxygen is always greater than that of carbon. The M subdwarfs (sdM) are the Population II counterparts, showing low metallicities and high space motions. Because they have smaller radii, they define a main sequence at lower luminosity than the M dwarfs for a given temperature. Hence the term subdwarf.

Type
Research Article
Information
International Astronomical Union Colloquium , Volume 146: Molecules in the Stellar Environment , 1994 , pp. 61 - 70
Copyright
Copyright © Springer-Verlag 1994

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