Ph.D., Astronomy, 1955; D.Sc., Astronomy, 1968, Charles University Prague.
Professor Plavec is interested in the bizarre cases of strongly interacting binary systems. The component stars in such systems strongly affect and often completely change each other's evolution by mass transfer, caused either by Roche lobe overflow or by a powerful stellar wind. In most cases, an extensive accretion disk forms around the mass-gaining component. However, a significant part of the transferred mass is not accreted but rather escapes into space: thus the interacting binaries enrich the interstellar medium, often by gas that was formerly processed in the CNO bi-cycle in the interior of the loser. The search for the accretion disks and the escaping matter is best done spectroscopically in the ultraviolet, so Professor Plavec was an ardent observer with the International Ultraviolet Explorer satellite, while it lasted (1978-1996). More recently, he used the Hubble Space Telescope to study the UV emission lines in one of his pets, called UX Monocerotis. An accretion disk and a mass-transfering stream have imprinted their spectral lines upon the spectra of the component stars. Plavec also models accretion disks and synthetic stellar spectra in collaboration with Dr. I. Hubeny (USRA). And since many interacting binaries hide their identity in dense circumstellar envelopes, Professor Plavec looks with suspicion at many stars displaying emission lines or circumstellar absorptions.