Summary: A&A manuscript no.
(will be inserted by hand later)
Your thesaurus codes are:
08 (08.01.3; 08.03.4; 08.12.1; 02.12.1)
Helium lines in latetype dwarfs.
A. C. Lanzafame ? and P. B. Byrne
Armagh Observatory, Armagh BT61 9DG, N. Ireland, UK
Received xxx; accepted xxx
Abstract. We analyse the formation of He I lines in latetype dwarfs by statistical equilibrium (or NLTE radiative
transfer) computations. Atmospheric models for dK (fflEri) and dMe V1005 Ori (=Gl 182) stars are considered. The va
lidity of the weakly nonuniform approximation for dMe stars established in Lanzafame (1994a) for the lower transition
region of dMe stars implies that streaming particles have virtually no role in the formation of the lines. Comparison
with observations of the He I (10 830 š A) and He I (5 876 š A) lines in the dMe star, V1005 Ori, indicate that it is pos
sible to reproduce the observed helium lines with a simple model compatible with other observational constraints.
Overionisation by coronal EUV radiation is found to play a minor role in the formation of the triplet lines.
Key words: Stars: atmospheres -- Stars: chromospheres -- Stars: latetype -- Lines: formation