Theory and Observations of Classical Novae

This review is mainly concerned with the physical nature and eruptive behavior of the classical nova outburst. Whether or not an eruptive variable can be considered a classical nova is most easily determined by both the optical light curve and spectral developments during the outburst. For the purposes of this review a star is defined as a classical nova if: 1. the optical brightness increases by > 9 mag in less than a few days; 2. significant brightness changes occur on a time scale of 10 00 days or less; 3. its spectral development can be classified in terms of the character­ istic nova stages [see the synthetic spectra by McLaughlin reproduced on pp. 135-36 in Hynek (1 951) or by Hack & Struve (1 970), pp. 16 8-69J; and 4. the spectra imply that matter is ejected with velocities greater than 100 km sec -1 and less than 5000 km sec -1. For more detailed discussion of empirical membership criteria, the reader is ref erred to Chapters 1 and