Nova Cygni 1975
I have a few separate remarks and preliminary results to report on Nova Cygni 1975, based on spectrographic observations made in Victoria. 1) We have performed an analysis of line profile changes similar to that made by Campbell (1976) for several nights on which many spectrograms were obtained, between Aug. 31 and Sept. 8. We find that analysis in terms of a simple pulsating model with the ∿ 3 hour period does not yield consistent results from night to night. Consequently we have investigated a more complex model in which a cosine modulated beam rotates in the centre of the nebula, to correspond to orbital motion of a hot spot in a conventional C.V. model. While there are many free parameters, it was found that such a model can reproduce all the profile changes studied and implies a smaller nebula and later “date of outburst” than Campbell’s model. 2) I want to make a point of noting the 2% change in the 3 hour period, which may imply considerable precession of a hot spot, and the possibly similar situation observed in VW Hyi. 3) We have attempted to follow the 3 hour modulation of line profiles late into the nebular stage, by performing Fourier analysis of spectrograms obtained in November 1975 and June 1976.