AN OPTICAL AFTERGLOW MODEL FOR BRIGHT LINEAR TYPE Ⅱ SUPERNOVAE

摘要

We show that a gamma-ray burst (GRB) afterglow model combined with an underlying plateau Type Ⅱ supernova can fit the data of at least one bright linear Type Ⅱ supernova, SN 1979C. We suggest that the bright linear subclass of Type Ⅱs could be represented by this model. We describe a scenario in which a hydrogen-rich massive star core collapses, causing a jet explosion that punctures through the star and initiates a shock that ejects the hydrogen-rich envelope. The jet is responsible for a low-density high-energy ejecta causing a GRB optical afterglow. The jet contains enough energy to create an asymmetric shock wave that ejects the He core and the overlying H envelope. We fit the observational data of SN 1979C with an analytic GRB model and a parameterized Type Ⅱ light curve from the data of SN 1969L. We also show that a numerical simulation of a massive star experiencing mass loss can also fit the data with ejected mass of 12 solar mass, initial radius ～300 solar radius, and explosion energy of 1 x 10~(51) ergs coupled to a GRB afterglow. We suggest that the energy of the jet could have been dissipated by the hydrogen envelope and thus not cause the ejecta to expand with the high velocities typically seen in Type Ic supernovae associated with GRBs. The model presented here could be an example of a failed GRB and X-ray flashes.