D. A. Green
Mullard Radio Astronomy Observatory, Cavendish
Laboratory, 19 J. J. Thomson Avenue,
Cambridge CB3 0HE, United Kingdom
Abstract. It has recently been suggested that the radio spectrum of the Galactic supernova remnant HB 3 shows flattening at higher frequencies (above about 1 GHz). Here I review the radio spectrum of HB 3, noting the difficulties in deriving accurate flux densities for this remnant, particularly at high frequencies, due to the proximity of bright, thermal emission from W3 and its surroundings. A flux density for HB 3 at 2695 MHz is derived from Effelsberg survey data. The spectrum of HB 3 is well represented by a simple power-law spectrum from 22 to 2695 MHz, with a spectral index of 0.56 +/-.03. It is concluded that contamination with thermal emission from adjacent regions is the cause for the reported spectral flattening of HB 3.
Keywords: supernova remnants - ISM: individual: HB 3 - radio continuum: ISM