The Evolution of Supernova Remnants in a Non-Uniform Medium

Abstract

We study the effect of multiple supernova explosions in a non-uniform interstellar medium using a two dimensional hydrodynamical code (axial symmetry assumed). Cooling effects were included. In a uniform medium two or more supernovae exploding at the same place but at different times result in a remnant with less energy than the sum of the individual explosion energies — when cooling effects are important. As a case of special interest the evolution of an OB association with many massive stars experiencing supernova explosions is presented. We show that it is difficult to produce large supershells with multiple supernovae alone, even if the sum of their explosion energies appear to be sufficient. The existence of a giant HII region preceding the explosions does not alter this conclusion. Other mechanisms should be considered to produce supershells.