Interpreting the Optical Nebular Spectrum of Nova Cygni 1992

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Session 29 -- Novae and Supernovae
Display presentation, Tuesday, 9:30-6:30, Pauley Room

[29.01] Interpreting the Optical Nebular Spectrum of Nova Cygni 1992

A. J. Barger, J. S. Gallagher, K. J. Bjorkman, J. S. Mathis, K. H. Nordsieck (U. Wisconsin-Madison)

The development of the optical spectrum of Nova Cygni 1992 has been monitored with a spectrophotometer on the 0.9-m telescope at the University of Wisconsin's Pine Bluff Observatory. These observations show that the nebular spectrum emerged about 50 days after visual maximum, and soon thereafter the H-Balmer series, He I, [O III], and especially [Ne III] emission lines dominated the optical spectrum. The great strength of [Ne III] indicates that this object has the optical spectral characteristics of a ``neon nova.'' As Nova Cygni has progressed into the nebular stage, the ionization level in the ejecta has steadily increased, e.g., as indicated by the ratio of He I to He II emission line intensities. In the 100 days [Ne V] spectrum has grown in intensity until it overwhelms all other optical emission lines, and [Fe VII] emission also has become pronounced. The physical interpretation of the spectrum is complex since the nova ejecta are clumpy, dense, and subject to an extraordinarily hard radiation field from the stellar nova remnant. On the other hand, Nova Cygni has been very well observed, and thus many paramters of the system are now constrained by multi-wavelength measurements. We will present results from our modelling study of the nebula of Nova Cygni, which is designed to obtain a first look at physical conditions within the nova ejecta, and to begin to address the issue of abundances in the nova ejecta.

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