GHRS and IUE Observations of Nova Cygni 1992: Watching the Veil Lift

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Session 53 -- Recent Observational Results on Nova Cygni 1992
Oral presentation, Wednesday, 1, 1994, 2:00-5:30

[53.04] GHRS and IUE Observations of Nova Cygni 1992: Watching the Veil Lift

S. N. Shore (IUSB), S. Starrfield (ASU), G. Sonneborn (GSFC/NASA), R. Gonzalez-Riestra (IUE/ESA), T. B. Ake (GHRS/CSC)

We have obtained ultraviolet spectroscopy and photometry of Nova Cygni 1992 = V1974 Cyg since its discovery was announced on 1992 Feb. 20. This talk will review the evolution of the UV spectra and how they disclose the physical conditions of the ejecta and the remnant. In particular, we will review the results from medium resolution (R=15000) GHRS observations of the optically thin stage of the outburst, 1992 Sep. 7 and 1993 Apr. 1, and discuss resultant models of the ejecta. The ejecta consist of slow moving filaments and fast moving diffuse material in an aspherical Hubble law-type outflow. The IUE observations show that the knots were present very early in the outburst and likely were frozen into the expanding medium at the moment of ejection. The line profiles display a striking velocity symmetry, especially in the filaments. Differential motion of the knots with respect to the background diffuse matter may be responsible for the observed hard component of the x-ray emission. The recent observations show that the density at almost two years into outburst (1993 Nov.) is still above $10^{7}$cm$^{-3}$, and that as the x-rays have turned off the shell has begun recombining. We will discuss predictions for structural changes in future imaging and we will discuss the interpretation of the structures already discovered in the FOC images of the ejecta.

Wednesday program listing