Many aspects of symbiotic stars have long puzzled astronomers. For instance while most students of the subject have considered them binary, many have at different times supported single star models. The nature of their outbursts is uncertain, while the dividing line between symbiotic stars and novae is unclear. In any case doubts can even be raised as to whether a class of "Symbiotic Stars" really exists. Much new data has been obtained in recent years, in particular from the study of radiation outside the visual region. Many symbiotic stars have been studied in the UV with IUE since 1978, while X-rays were det ected in a few cases with the Einstein satellite. There have been a num ber of infrared and radio studies, and the number of known symbiotic stars has also considerably increased. Furthermore theoretical ideas have in recent years been considerably enriched by concepts of stellar winds, and accretion phenomena in binaries including accretion disks. It was there fore extremely opportune and timely to hold the first international meet ing exclusively devoted to these stars, so as to consider the new results from such a wide range of observations in different spectral regions, and the conclusions which can be drawn for possible models as well as theories of the nature and structure of symbiotic stars. After a session devoted to new observations in different spectral regions, a session was spent considering some individual stars.

Proceedings of the IAU Colloquium No. 70, Observatoire de Haute Provence, 26-29 August, 1981

Inhalt
Fifty Years of Symbiotic Stars.- Introductory Report on Symbiotic Stars.- Session I New Observations of Symbiotic Stars.- Radio Observations of Symbiotic Stars.- Infrared Studies of Symbiotic Stars.- IR Photometry of Symbiotic Stars at Calar Alto Observatory.- Near IR Spectra of Symbiotic Stars.- Photographic Infrared Spectra of Symbiotic Stars.- Properties of Symbiotic Stars from Studies in the Optical Region.- Spectra of Individual Symbiotic Stars.- Visual Symbiotic Spectra Obtained with the Haute Provence Multiphot Detector.- UV Line Emission of Symbiotic Stars.- Ultraviolet Properties of the Symbiotic Stars.- X-Ray Observations of Symbiotic Stars.- X-Ray Detection of the Symbiotic Star Ag Draconis.- Session II Discussion on Individual Stars.- Z Andromedae: The Prototype?.- A Review of the Properties of the Symbiotic Star CH Cygni.- Recent Increase of the Activity of the Symbiotic Star CH Cygni.- Polarimetry of CH Cygni.- UV Eclipse Observations of CI Cyg.- IUE Observations of CI Cygni during 1979.- The Eclipse of CI Cygni in 1980 on the Objective Prism Spectra.- Variation Spectrale DE CI Cygni EN.- Spectral Variations of CI Cyg Between 1980 And.- Optical Observations of CI Cygni.- Introductory Report on V1016 Cygni.- Recent Studies of the Spectrum of V1016 Cygni.- The Peculiar Symbiotic Object V1329 Cygni: Single-Star Versus Binary Models.- Physical Properties of V1329 Cygni.- Variability of HBV 475 in the Near Infrared.- Spectral Evolution of HBV 475 (= V1329 Cygni) in the Ultraviolet.- Introductory Remarks on the Symbiotic Star AG Draconis.- The Ultraviolet Spectrum of AG Draconis.- Spectroscopic Observations of AG DRA.- UV Time-Dependent Emission in SY Muscae.- AR Pavonis: The Rosetta Stone of the Symbiotics.- Introductory Report on AG Pegasi.- The Peculiar Star RX Puppis.- Long Term Trends in the 3.5m Light Curve of RX Puppis.- HM Sagittae A most Remarkable Star.- Spectral Evolution of HM Sagittae in the Ultraviolet.- RR Telescopii.- Ultraviolet Observations of RR Telescopii.- V 4049 Sgr.- The Kuwano Peculiar Object (PU Vulpeculae).- Session III Interpretation.- Determination of the Term Symbiotic Star.- The Symbiotics as Binary Stars.- Models for Symbiotic Stars in the Light of the Data.- Symbiotic Star UV Emission and Theoretical Models.- Session IV Evolutionary Considerations.- The Evolutionary Status of Symbiotic Stars.- On the Model of Symbiotic Stars.- Concluding Remarks.- Star Index.