A numerical model for Cassiopeia A (3C 461).

Numerical models have been constructed to determine possible fits to the supernova remnant Cassiopeia A. The range of parameters is narrowed considerably by making use of the ratio of the radio-emitting shell to the remnant radius. It is also shown that the velocity of expansion of the remnant is probably between 1000 and 3000 km/s, and that the peak of the nonthermal radio emission is most likely associated with the interface between the ejected and accreted shells.