INHOMOGENEITIES IN TYPE Ib/c SUPERNOVAE: AN INVERSE COMPTON SCATTERING ORIGIN OF THE X-RAY EMISSION

Inhomogeneities in a synchrotron source can severely affect the conclusions drawn from observations regarding the source properties. However, their presence is not always easy to establish, since several other effects can give rise to similar observed characteristics. It is argued that the recently observed broadening of the radio spectra and/or light curves in some Type Ib/c supernovae is a direct indication of inhomogeneities. As compared to a homogeneous source, this increases the deduced velocity of the forward shock and the observed correlation between total energy and shock velocity could in part be due to a varying covering factor. The X-ray emission from at least some Type Ib/c supernovae is unlikely to be synchrotron radiation from an electron distribution accelerated in a nonlinear shock. Instead it is shown that the observed correlation during the first few hundred days between the radio, X-ray, and bolometric luminosities indicates that the X-ray emission is inverse Compton scattering of the photospheric photons. Inhomogeneities are consistent with equipartition between electrons and magnetic fields in the optically thin synchrotron emitting regions.