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Session 27 - Variable Stars, Novae, & Supernovae.
Display session, Tuesday, June 10
South Main Hall,
The evolution of a supernova remnant through the transition from an adiabatic Sedov-Taylor blastwave to a radiative pressure-driven snowplow phase is studied using one and two-dimensional hydrodynamic simulations over a range of upstream densities between 0.2 and 200 cm^-3. This transition is marked by a catastrophic collapse of the post-shock gas, forming a thin, dense shell behind the forward shock. Our 1D results show that at late times, the shock front is characterized by an expansion parameter Vt/R\approx 0.33, considerably higher than the analytic estimate of 2/7 for a pressure driven snowplow. Shortly after the transition, the forward shock is subject to an overstability of the postshock cooling region. However, we find that oscillations from this overstability quickly damp out if the ambient density \lesssim 1 \ cm^-3. The thin shell is also expected to be subject to various non-radial instabilities, including the pressure driven thin shell instability and the non-linear thin shell instability. In our 2D simulations, we find that small perturbations do not have enough time to grow significantly before the blastwave decelerates below a Mach number of 3. However, relatively large perturbations ( \gtrsim 1 % ) can significantly distort the overall morphology of the shell.
Program listing for Tuesday