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S. Starrfield (ASU), F. X. Timmes (Chicago), W. R. Hix (ORNL), E. M. Sion (Villanova), W. M. Sparks (LANL), S. Dwyer (ASU)
Nova explosions occur on the white dwarf (WD) component of a Cataclysmic Variable stellar system which is accreting matter lost by a companion. A type Ia supernova is thought to result when the WD, with the same configuration, grows in mass to the Chandrasekhar Limit. Here, we present the first self-consistent calculations of accretion onto massive WDs which demonstrate that this evolution can occur. In this study, we have investigated the accretion of Solar matter at high mass accretion rates onto hot, luminous, WDs (L>30L\odot). We use the 1D, hydrodynamic, computer code described in Starrfield et al. (APJS, 127, 485, 2000) plus a nuclear reaction network found at {\tt http://flash.uchicago.edu/fxt/code-pages/net-pphotcno.shtml}. In contrast to our nova simulations, where material is ejected at high velocities \it only when the WD has a low luminosity and the rate of mass transfer onto the WD is < 10-9M\odot yr-1, these simulations do not eject material and the WD grows in mass. Our simulations also show that a hydrogen thermonuclear runaway does not occur since hydrogen fuses immediately to helium in the surface layers. As the helium ash grows in mass, it gradually fuses both to carbon and more massive nuclei depending on the WD mass and mass accretion rate. Moreover, the surface conditions of our simulations agree with observations of the Super Soft X-ray binary sources. Our results, therefore, confirm previous suggestions that some of the Super Soft X-ray binaries (CAL 83 and CAL 87, for example) may be the progenitors of SN Ia explosions. S. Starrfield acknowledges support from NSF and NASA grants to ASU. FXT is supported by DOE under Grant No.~B341495 to the Center for Astrophysical Thermonuclear Flashes at the University of Chicago. EMS is supported by NASA ADP grant NAG5-11182.
The author(s) of this abstract have provided an email address for comments about the abstract: starrfie@susie.la.asu.edu
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.