Recent advances in studies of the nova outburst

The nova outburst is a consequence of the accretion of hydrogen-rich material onto a white dwarf in a close binary system and observations show that the accreting material must have mixed with core material at some phase of the outburst. Abundance determinations of novae ejecta show that the core material is either carbon and oxygen or oxygen, neon, and magnesium. I report on the methods and results of a project to determine the ejecta abundances for a number of recent Galactic and LMC novae using combined optical and ultraviolet data. The abundance determinations also provide a value for amount of mass ejected in the outburst. There are large discrepancies between the observed and predicted values of the ejecta mass in that the observed ejecta masses are much larger than predicted for both carbon-oxygen and oxygen-neon-magnesium novae. I also review the X-ray observations and present new evolutionary calculations done to try to understand the missing ejecta mass problem and suggest a possible solution to this problem. (C) 1999 Elsevier Science B.V. All rights reserved.