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Optical Chromospheric Spectral Lines in K and M Dwarf Stars

Published online by Cambridge University Press:  27 September 2017

R.D. Robinson  and
L.E. Cram
R.D. Robinson
Affiliation:
Anglo-Australian Observatory
L.E. Cram
Affiliation:
University of Sydney

Abstract

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Observations are reported of the Ca II resonance lines and II α in dK and dM stars, made with high S/N ratio and high spectral resolution. Ca II emission is found in all stars observed, and those having weak Ca II exhibit marked Hα absorption. It is found that the strengths of the two kinds of chromospheric, lines are not tightly correlated, an effect which can be shown to be independent of the effective temperature of the stars. The result implies that a one-parameter description (e.g. heating rate) of the chromospheres is not viable. While lateral inhomogeneities are likely to be an important second parameter, we also suggest that the Hα line may be formed in a region considerable higher that in which the Ca II lines are formed.

Type
Session I: Stellar Flares
Information
International Astronomical Union Colloquium , Volume 104 , Issue 2: Solar and Stellar Flares , 1989 , pp. 75 - 78
Copyright
Copyright © Kluwer 1989

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