On the Sensitivity of Deflagrations in a Chandrasekhar Mass White Dwarf to Initial Conditions

We analyze the sensitivity of the flame propagation in a Chandrasekhar masswhite dwarf to initial conditions during the subsonic burning phase, using 2Dsimulations of the full WD. Results are presented for a wide variety of initialflame distributions including central and off-center single point andmulti-point, simultaneous and non-simultaneous, ignitions. We also examine theeffects of convective velocity field which should exist at the core before thethermo-nuclear runaway. Our main conclusion suggests that the amounts ofburning products and their distributions through the deflagration phase areextremely sensitive to initial conditions, much more sensitive than presentedin previous studies. In particular, we find that more complex configurationssuch as even slight off-center ignitions, non-simultaneous multi-pointignitions and velocity fields tend to favor solutions in which individualplumes rise faster than the bulk of a typical Rayleigh-Taylor driven, unstableburning front. The difference to previous calculations for an octant of a WDmay be understood as a consequence of the suppression of l=1,2 modes. Ourresults are consistent with full star calculations by the Chicago group.Moreover, the total amount of nuclear burning during the phase of subsonicburning depends sensitively on the initial conditions and may cause the WD topulsate or to become unbound. We discuss the implications of the results oncurrent models for Type Ia SNe, limitations imposed by the 2-D nature of ourstudy, and suggest directions for further study.Comment: 13 pages, 5 figures, ApJ submitte