SYNCHROTRON SELF-ABSORPTION OF RADIO-EMISSION FROM SUPERNOVAE

The low-frequency cutoff in the radio spectra of supernovae may be due to synchrotron self-absorption. For four out of six supernovae investigated, the angular size estimate based on synchrotron self-absorption is the same, to within the errors, as the size derived from the shell expansion velocity. The angular size of two type Ib supernovae obtained from self-absorption is 5-7 times smaller than the size given by the expansion velocity. This discrepancy can be disposed of by assuming that the radio shell is expanding much more rapidly than the optical shell. We predict the specific behavior of the degree and position angle of linearly polarized radio emission from supernovae.