The Optical Spectrum of Nova Cygni 1992

Spectroscopy of the ONeMg nova Cygni 1992 is presented, based on data obtained \nat the Vainu Bappu Observatory between 1992 March l3-May 22 and \n1993 January 3. Spectra were obtained at five epochs- epoch I: 1992 March \n13-14, 20 days after the outburst maximum; epoch II: 1992 March 22-24, 30 \ndays after maximum; epoch III: 1992 April 20, 58 days after maximum; epoch \nIV: 1992 May 21-22, 90 days after maximum; and epoch V: 1993 January 3, 347 \ndays after maximum. The spectrum during epochs I-II is dominated by strong \nbroad P -Cygni emission lines predominantly of hydrogen Balmer and Fe II lines. \nLines due to N II, Mg II and He I are also strong. [OI] auroral and nebular lines \nare also present. In the red region of the spectrum, 0 17774,8446 and lines due \nto Mg II, N I and Ca II are strong, with the strength of 0 I 8446 line indicating \nLyf3 fluorescence and a high optical depth. Epochs III-V show It steady increase \nin the strength of He I and [O III] lines, while the strength of the other permitted \nlines steadily decreases. On day 347, [O III] 4959+5007 is 3 times stronger than \nHalpha and 8 times stronger than Hp.