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Session 79 - CVs and Novae.
Display session, Wednesday, January 17
North Banquet Hall, Convention Center
We report on the results of new calculations of Thermonuclear Runaways (TNR) on 1.25M_ødot and 1.35M_ødot oxygen-neon-magnesium white dwarfs using an updated version of \tt NOVA. \tt NOVA is a one-dimensional, fully implicit, hydrodynamic stellar evolution code that includes a large nuclear reaction network. The results of our previous studies can be found in Starrfield et al (1992, ApJ, 391, L71) and Politano et al (1995, ApJ, 448, 807). Since those calculations were done, we have updated both the nuclear reaction network and the nuclear reaction rates (see, for example, Van Wormer et al 1994, ApJ, 432, 326 and Herndl et al 1995, Phys. Rev. C, 52, 1078). We now use opacities from the OPAL carbon rich tables. When we are outside the range of validity of the OPAL tables, we continue to use the Iben fit. The new sequences also include boundary layer heating both from the accretion shock and the internal energy of the infalling material (Shaviv and Starrfield 1987, ApJ, 321, L51). Finally, in order to improve the agreement between our theoretical light curves and the observations, we use bolometric corrections obtained from the latest generation of spherical, expanding, Non-LTE, stellar atmospheres for novae (Hauschildt et al 1995a, ApJ, 447, 829; Hauschildt et al 1995b, ApJ, in press). Our first results show that the changes in the reaction rates and the opacities cause quantitative changes with respect to our published studies. For accretion onto the 1.25M_ødot white dwarf, for example, we find that less mass is ejected and a smaller amount of ^26Al is produced. In addition, the abundances of ^31P and ^32S increase by factors of more than two. The causes are that the OPAL opacities are larger than those given by the Iben fit, which results in less mass being accreted on the white dwarf for the same initial conditions, and (2) the proton-capture reaction rates for some of the intermediate mass nuclei near ^26Al have increased so that the evolution to higher mass nuclei is enhanced. We acknowledge partial support by DOE, NASA, and NSF.
