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Session 47 - Novae.
Display session, Tuesday, January 14
Metropolitan Ballroom,

[47.01] The Spectroscopic Evolution of Nova Cygni 1992

A. Moro-Martin (MMO/U.Complutense), P. M. Garnavich (CfA), A. Noriega-Crespo (IPAC/MMO), A. Alpert (MMO)

Optical spectroscopic observations of Nova Cygni 1992 spanning 4 years are modeled in this study. The data were obtained primarily with the DAO 1.8m telescope and cover a wavelength range from \sim 3200 - 8000 ÅThe observations begin on May 92 (85 days after the outburst) and end on June 1996, i.e. during most of the optically thin evolutionary phase. The spectra were modeled in a relatively straightforward way by using the flux predicted by a photoionization code [1] for most of the emission lines (down to 0.1a synthetic spectrum. There are, however, significant differences in the detailed procedure in comparison with similar works [2]. First, the photoionization models were run at a fixed abundance value for the most prominent elements (i.e. H, He, C, O, N, Ne, Fe, etc) over the entire time sequence. Second, the brightest lines, e.g. [Ne V], [Ne III], [O III] and the Balmer lines, were initially used as guide to match the observations. The rest of the spectra, which includes the fainter lines, were then directly predicted by the photoionization code. Considering the complicated structure of the shell [3], the lack of well defined values of its gas density and our limited knowledge of the time evolution of the surface temperature of the photoionization source, the comparison between models and observations agrees remarkably well. It was found that the time evolution of some of the Iron coronal lines, [Fe VII] 6087 Åand [Fe X] 6374 Åclosely follows that of the X-rays [4]. [1] Ferland, G.J 1993, CLOUDY, U. of Kentucky Dept. Phys amp; Astr. Internal Report. [2] Austin et al. 1992, AJ, 111, 869 [3] Paresce, Livio, Hack amp; Korista (1995) Aamp;A, 299, 823 [4] Krautter et al. (1996), ApJ, 456, 788

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