Nova Delphini 1967. II. Physical properties and element abundances in the nebular state

Physical properties of the Nova Delphini 1967 during its ''nebular'' stages are derived from high dispersion spectra taken during the period 1967 July to 1969 August. The electron temperature and electron density were determined from the ratio of auroral to nebular line intensities of [O iii] and [N ii]. During the summer of 1969, values on the order of T/sub e/=13,300 K and N/sub e/=1.74 x 106cm-3 were obtained. In addition, on certain dates it was possible to determine a separate electron temperature for different components of the [O iii] line profile; that is, for different ejections of the nova. We have determined the oxygen and helium abundances for the nebulosity. The ratio N(O)/N(H) is approximately solar, in conflict with earlier determinations for this object, while N(He)/N(H) approx. =0.20 by number; the oxygen determination is in agreement with recent calculations by Sparks et al. Some possible reasons for earlier determinations of oxygen over-abundance are discussed. The existence of self-absorption in the He0 spectrum is noted. From Hβ photometry, the mass of the nebula is determined to be 2.9 x 1030 g, or less if there is self-absorption in the Balmer spectrum. A classification of emission lines by shape is carried out, and a discussion of one aspect of line intensity variations with time is carried out, namely, a comparison with time of the ratio of [O iii] lambda5007 intensities between the two principal ejections