Portal de Periódicos da CAPES

Capítulo de livro Produção Nacional Revisado por pares

BIBTEX RIS

Helium Lines Formation in T-Tauri Stars

1988; Springer Nature (Netherlands); Linguagem: Inglês

10.1007/978-94-009-2951-7_51

2214-7985

R. de la Reza, Natalie M. Batalha,

Astrophysics and Star Formation Studies

The NLTE formation of the He I lines λλ 10830, 5876 and the He II lines λλ 304, 256, 1640 and their respective continua in T-Tauri stars is investigated. For this purpose a NLTE model of a deep chromosphere has been developed in which hydrogen is the principal electron donor. H ionization is calculated considering the Ly continuum and Lyα, Lyβ, Hα and Hβ lines. The He II lines are formed at temperature between 2×105K and 5×1O4K being collisionally controlled. We put in evidence that the proper He II resonance radiation λ 304 dominates the He I ionization at < 504 Å by means of an overlapping of both radiations. Photoionization and ionization by collisions followed by recombinations are the most important mechanisms populating the levels producing the He I emission lines λλ 5876 and 10830. Nevertheless the principal source of ionization is the λ 304 radiation being ultimatelly controlled by collisions. In T-Tauri stars neutral lines appear then not to be good indicators of hot coronae.