Resonance broadening and van der waals broadening

Institute of Astronomy, Russian Academy of Science, Pyatnitskaya 48, 119017 Moscow, Russia
e-mail: lima@inasan.ru

Abstract

Resonance broadening is important for the hydrogen lines in the spectra of F-type and later stars. In the corresponding temperature regime, the extended wings of the Balmer lines are used as a stellar effective temperature indicator. We show the effect of the use of two broadening theories, Ali & Griem (1965, 1966) and Barklem et al. (2000a, 2000b), on the effective temperature derived in non-LTE from H_α and H_β in the Sun and the metal-poor star HD19445. Van der Waals broadening is important for strong spectral lines in the atmospheres of F-type and later stars. For the selected transitions in Ca I and Ca II, line profile comparisons are made between applying the van der Waals damping constants from laboratory measurements, the ABO perturbation theory, and the classic Unsöld approximation.