Helium Lines in Late-type Dwarfs
نویسنده
چکیده
We analyse the formation of He I lines in late-type dwarfs by statistical equilibrium (or NLTE radiative transfer) computations. Atmospheric models for dK (Eri) and dMe V1005Ori (=Gl 182) stars are considered. The validity of the weakly non-uniform 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 A) and He I(5 876 A) lines in the dMe star, V1005Ori, indicate that it is possible to reproduce the observed helium lines with a simple model compatible with other observational constraints. Over-ionisation by coronal EUV radiation is found to play a minor role in the formation of the triplet lines.
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