Non-equilibrium ionisation in supernova remnants : the case of Tycho.

Abstract

A detailed numerical study of the X-ray emission of Tycho's supernova remnant which, at an age of about 430 years, has not yet reached its adiabatic phase of expansion. The carbon deflagration of a C + O white dwarf, which seems to be the most plausible model for type Ia supernova explosions, results in a highly nonsolar abundance distribution, which influences the hydrodynamical evolution of the remnant considerably. Using Nomoto's W7 model of an exploding white dwarf as initial condition, the hydrodynamical and ionization evolution for different densities of the interstellar medium are followed simultaneously and the emitted spectra are compared with Exosat GSPC observations. The results indicate that the density of the ambient medium is between 0.5 and 1.0/cu cm; the distance of Tycho is then about 3 kpc.