It has recently been suggested that the radio spectrum of the Galactic supernova remnant HB3 shows flattening at higher frequencies (above about 1GHz). Here I review the radio spectrum of HB3, 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 HB3 at 2695 MHz is derived from Effelsberg survey data. The spectrum of HB3 is well represented by a simple power-law spectrum from 22 to 2695 MHz, with a spectral index of 0.56 pm 0.03. It is concluded that contamination with thermal emission from adjacent regions is the cause for the reported spectral flattening of HB3.
Bulletin of the Astronomical Society of India
- Pub Date:
- June 2007
- supernova remnants;
- ISM: individual: HB3;
- radio continuum: ISM;
- Accepted for publication by the Bulletin of the Astronomical Society of India