Thermal Radio Emission of Supernova Remnants: The Spectrum of HB3

Abstract

An analysis of the broadband radio spectrum (from 38 MHz to 3.9 GHz) of the Galactic supernova remnant (SNR) HB3 (G132.7+1.3) is presented. A single synchrotron component appears to be insufficient to adequately fit the radio spectrum of this source, because of the obvious spectrum curvature at the higher radio frequencies. The simulated spectrum using a combination of a synchrotron component and a thermal bremsstrahlung component is presented. We also discuss properties of this latter component and estimate the ambient density implied by the presence of this component to be n ~10-40 cm^-3.