Poonam Chandra1,2 and Alak Ray2
1 Joint Astronomy Programme, IISc, Bangalore 560012
2 Tata Institute of Fundamental Research, Mumbai 400005
Abstract. We emphasize the importance of observations of young supernovae in wide radio band. We argue on the basis of observational results that only high- or only low-frequency data is not sufficient to get full physical picture of the shocked plasma. In SN 1993J, the composite spectrum obtained with Very Large Array (VLA) and Giant Metrewave Radio Telescope (GMRT), around day 3200, shows observational evidence of synchrotron cooling, which leads us to the direct determination of the magnetic field independent of the equipartition assumption, as well as the relative strengths of the magnetic field and relativistic particle energy densities. The GMRT low-frequency light curves of SN 1993J suggest the modification in the radio emission models developed on the basis of VLA data alone. The composite radio spectrum of SN 2003bg on day 350 obtained with GMRT plus VLA strongly supports internal synchrotron self absorption as the dominant absorption mechanism.
Keywords: magnetic fields - radiation mechanisms: non-thermal - radio continuum: stars - supernovae: individual (SN 1993J, SN 2003bg)