Xiaping

The kinematic evolution of a non-radiative supernova remnant (SNR) is characterized by the transition from an ejecta dominated phase to an ambient medium dominated phase. The asymptotic behaviors of the remnant in the early ejecta dominated phase, when swept up ambient medium mass is negligible, and the late ambient medium dominated phase, when ejecta mass becomes negligible, have already been extensively studied. It is well known that in early ejecta dominated phase, the evolution of the SNR simply follows the free expansion solution or the self similar driven wave solution depending on the density profile of the ejecta. In the late ambient medium dominated phase, the evolution of the SNR asymptotically approaches the Sedov-Taylor solution. But in reality observed young non-radiative SNRs are always in transition from one asymptotic solution to the other, so it is essential to understand the transition between phases. We present a new approach based on dimensional analysis to derive an analytical solution describing the kinematic evolution of a SNR during the transition. Since no assumption for the dynamical structure within the remnant is required, the solution is simplified compared to previous work (e.g., Truelove & McKee 1999, TM99). We compared our solution with the TM99 solution and 1D numerical simulation results for both a uniform density medium and a wind density profile ambient medium. For all our cases, the age calculated from our analytical solution at a certain radius is consistent with the numerical simulation to an accuracy of a few percent and provides a better fit than the TM99 solution.