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Formation of the Optical Spectra of the Coolest M- and L-dwarfs and Lithium Abundances in their Atmospheres

Published online by Cambridge University Press:  25 May 2016

Yakiv V. Pavlenko
Yakiv V. Pavlenko*
Affiliation:
Main Astronomical Observatory of NAS, Golosiiv woods, 03680, Kyiv-127, Ukraine

Abstract

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Theoretical aspects of modeling of spectra of late M- and L-dwarfs are discussed. We show, that the processes of formation of spectra of M- and L-dwarfs are basically different. Instead of the case of M-dwarfs, atoms of Ti and VO should be depleted into grains in the atmospheres of L-dwarfs. Overall shape of the L-dwarf spectra is governed by the K I + Na I resonance line wings of the huge strength. To fit lithium lines observed in spectra of the coolest dwarfs we used two additional suggestions: a) there are some extra depletions of molecular species absorbed in the optical spectra of L-dwarfs; b) there may be (a few?) additional (“dusty”?) opacity sources in their atmospheres. Problems of lithium line formation and the “natural” limitation of their use for the ‘lithium test’ for the case of L-dwarfs are discussed.

Type
6. Stellar Knowledge to and from Light Elements
Information
Symposium - International Astronomical Union , Volume 198: The Light Elements and their Evolution , 2000 , pp. 454 - 459
Copyright
Copyright © Astronomical Society of the Pacific 2000 

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