Michael Friedjung Though known since antiquity, novae are still poorly under­ stood and present many problems. There has tended to be a lack of communication between theoreticians and observers and between different schools of thought, in spite of the advances of recent years in certain directions (observations of ordinary novae at minimum and of dwarf novae, theory of the causes of the explosion, etc ... ). The meeting whose proceedings are contained in this volume was organized to stimulate a confron­ tation between the different ideas and results. The subject has changed a lot since 1963, when the previous international meeting was held. There were 61 participants at the conference from 17 countries, so very many groups ~oing research in the field of novae were represented. The reader will see that the subject has become more physical (we know for instance that the binary nature of novae is essential) but much work remains to be done. There is still a large gulf between theory and observation. May he find here many new ideas for future research! I would like to thank the French Centre National de la Recherche Scientifique for providing financial help. I must also thank the other members of the scientific committee (Profs and Drs Bath, Mustel, Payne-Gaposchkin, Sparks and Warner) and of the local committee (Audouze, Mrs Steinberg, Vauclair).

Inhalt

I: Novae, Dwarf Novae and Similar Objects at Minimum Light.- Introductory Reviews.- Past and Future Novae.- Observations of Novae and Related Objects at Minimum Light.- Mass Transfer and Accretion Disc Flow in Close Binary Systems.- Transfer Instabilities and Accretion Disc Structure in Dwarf Novae.- Short Contributions.- On the Stability of Accretion Disks.- Recent Photometric Observations of Nova-Like Variables.- Cross Correlation Detection of Rapid Stellar Variability Using Two Telescopes.- The Binary Nature of Tee Nova-Like Variable CD-42° 14462.- Relation of the X-Ray Sources Sco X-1 and Cyg X-2 to Old Novae.- Model of u Geminorum.- The Continuous Radiation Emitted by the Accretion Disks in Cataclysmic Binaries. The Dwarf Nova SS Cyg During Outburst at the Old Novae V603AQL.- II: Observations of Novae and Related Objects During Outburst.- Introductory Reviews.- Models of the Nova Outburst.- The Expansion of Novae Before Light Maximum and the Formation of the Principal Envelope.- Short Contributions.- The Variable Radial Velocity of He I 5876 in the Spectrum of Nova Delphini 1967 /HR Del/.- Model of Nova Envelopes.- "Bloated Dwarf" Model of Nova Light Curves.- Physical Parameters of Prenovae and Outburst Amplitudes.- Timing of the Shell Ejection in Nova Outbursts.- Nova FH Serpentis as a Test of Outburst Model.- Spectroscopy of the Nova Vulpeculae 1968 No. 1 (LV Vul).- Grain Formation in Nova Envelopes.- III: (a) Nebular Stage of Novae.- Introductory Reviews.- Problems of Ionization of Nova Envelopes in the Nebular Stage. The Models for Nova Delphini 1967.- Abundances Determinations in the Nebular Stage of Novae.- Short Contributions.- Spectral Evolution of Nova HR Del During Its Decline Towards Minimum.- The Light Curve of DQ Herculis 1934.- Evidences for the Development of a Collisional Spectrum in the Nebular Stage of Novae.- The Slow Nova RR Tel and the Symbiotic Stars.- (b) Transient X-Ray Sources.- Short Contributions.- Optical Properties of X-Ray Novae.- The 8-Day Modulation in V616 Mon (A0620-00).- The X-Ray and Optical Light Curves of A0620-00 (V616 Mon).- Spectroscopic Observations of V616 Mon (A0620-00).- A Note on the Spectrum of V 616 Monocerotis.- Session Summary.- IV: Observations of Nova Cygni 1975.- Introductory Review.- Observations de Nova Cygni 1975 (V 1500 Cyg).- Short Contributions.- Spectrophotometric Study of the Continuous Spectrum of Nova Cygni 1975 (V 1500 Cyg).- Nova Cygni 1975.- Multi-Band Photometry of Nova Cygni 1975.- Clues to the Binary Nature of Nova Cyg 1975.- Spectral Evolution of Nova V 1500 Cyg (1975) from September 1975 to May 1976.- Model of a Nova Outburst on the Basis of Measurements on V1500 Cygni.- Pre-Maximum Spectra of V1500 Cygni.- Ultraviolet Photometry of Nova Cygni 1975.- Nova Cygni 1975 as a Classical Thermonuclear Runaway Event.- Session Summary.- V: Theories of the Causes of Outbursts.- Introductory Reviews.- A Review of the Thermonuclear Runaway Model of a Nova Outburst.- Nucleosynthesis Induced During Nova Outburst.- Short Contributions.- Optically Thick Winds in Classical Novae and Symbiotic Stars.- Thermal Runaway Near the Surface of Accreting White Dwarfs.- The Slow Nova.- The Evolution of a Nova Model with a Z=.03 Envelope from Pre-Explosion to Extinction.- Hydrogen-Rich Envelope Mass -- A Vital Nova Parameter.- Session Summary.- VI: Future Work.- Session Summary.