Theoretical profiles of the HeII 1640 line in expanding atmospheres of hot stars

VENERO, R.; CIDALE, L.; RINGUELET, A.

Kyoto

Congreso; Spectroscopy with Large Telescopes of Chemically Peculiar Stars; 1997

IAU

A calculation of theoretical profiles of the HeII lambda 1640 line for hot stars with an expanding and spherically symmetric model atmosphere has been performed. Making use of the Feautrier´s method, the radiative transfer equation has been rigorously solved in the comoving frame and spherical coordinates, simultaneusly with the statistical equilibrium equations in the equivalent two-level-atom aproach. Line formation regions and relations between profile shapes and free parameters of temperature and velocity distributions have been studied, to discuss the relevance of the HeII lambda 1640 line as a diagnostic tool for the the physical conditions of extended atmospheres.