Astronomy

TOPIC A : Extended Atmospheres (Van Rensbergen W.) - - Atmospheres of early type stars. Computer codes have been developed to calculate non LTE radiative transfer in extended atmospheres; the structure of these atmospheres; occupation numbers of atomic energy levels in these atmospheres; P-Cygni line spectra observed from early type stars with stellar wind; three dimentional line transfer for Be Star envelopes; active Stark effect in atmosheres of early type main sequence stars. Implemantation of these codes on MIDAS enbable comparison with observations. - - TOPIC B : Stellar Structure and Evolution (De Grève J.P.) - - Evolution of massive close binary systems. A computer code was developed allowing the simultaneous calculation of the structure and evolution of a binary system as a result of the evolution of the individual components as well as a result of changes of this evolution due to gravitational interaction between them. The applied research concentrates on early-type stars,Wolf Rayet stars and semidetached binaries. : Structure and Evolution of WR- binaries : Star Formation and Early Stellar Evolution - - TOPIC C : Observation of Stars: Photometry and Spectroscopy (Sterken C.) : Observations and analyses are carried out on the variability of b Cephei stars, LBV's, d Scuti stars, WR stars, Ap stars. : Long Term Photometry Variables Observing Programme.