PARAMETRIZED STARK PROFILES OF HYDROGEN LINES IN HOT STELLAR PLASMAS

Profiles of the neutral hydrogen lines, in the Lyman and Balmer series, are presented for an extended range of physical conditions which are met in radiative envelopes of A and F stars. Detailed Stark profiles are computed using the Model Microfield Method and including the dynamical effects for electrons and ions. The new theoretical profiles are compared with previous available data which are currently used in astrophysical applications. The effect of the thermal Doppler broadening and the asymptotic behaviour in the wings are discussed. Systematic trends of the profiles are studied inside each series, with increasing temperature and density. They lead to fit each profile with a simple analytic function using four parameters. These parameters are given as analytic functions of the temperature and the electronic density, in the range T = 10(4)-10(5) K and n(e) = 10(14)-10(17) cm-3, for eight lines in the two series. This provides an easy way of deriving any Stark profile in a wide range of plasma conditions and with an accuracy better than 20%. Examples of application to the detailed hydrogen opacity in stellar envelope are shown.