[Previous] | [Session 86] | [Next]
S. Starrfield, G. J. Schwarz (ASU), J. W. Truran (Chicago), W. M. Sparks (LANL)
The nova outburst is the consequence of a thermonuclear runaway in the accreted hydrogen rich envelope on the white dwarf component of a close binary system (Cataclysmic Variable). The amount of material accreted onto the white dwarf is determined by the competition between the rate at which energy is produced in the accreted layers (initially by the proton-proton reaction chain) and the rate at which it is transported away from the nuclear burning region by a combination of electron conduction and radiation diffusion. Clearly, the opacity is an important parameter in this competition since the larger the opacity, the larger the amount of heat trapped in the nuclear burning region, and the more rapid the rise in temperature. Because of the presence of novae far from the Galactic plane and in the Magellanic Clouds, it is important to study the evolution of the outburst in material that has a sub solar metallicity. For example, the super-Eddington nova LMC 1991 has a metallicity of less than a tenth of Solar (Schwarz et al. BAAS, 30, 1400, 1998). We have now done hydrodynamic evolutionary calculations, using the OPAL opacities, for both 1.00M\odot and 1.25M\odot white dwarfs accreting material with either Z=0.02 or Z=0.001. We have used two mass accretion rates and two initial white dwarf luminosities to study a variety of initial conditions. As predicted (Starrfield et al. MNRAS, 296, 502, 1998), we have found that lowering the metallicity increases the amount of material accreted onto the white dwarf. The larger amount of accreted material drives the TNR to higher peak temperatures and more material is ejected at higher velocities. This difference is more apparent at the larger white dwarf mass. We will present the detailed results of our evolutionary sequences. This research was supported by the NSF, NASA, and the DOE in grants to our various institutions.
If the author provided an email address or URL for general inquiries, it is a
s follows:
http://brian.la.asu.edu