Supernova Explosions and Their Ejected Shells

Abstract

There is an increasing awareness that SN explosions may not be driven by neutrinos and/or photons but by the spin motion of the collapsing core, transferred via magnetic viscosity to the shell. On reconnection, the magnetic spring will convert its remaining energy into pair plasma. It is not clear at this time whether SNe of type Ia should be excepted from this scheme: there simply are too many neutron stars.

Supernovae have mechanical energies of 10^{5 1 ± 0.5} erg, some 2% of the collapsing core’s maximal spin energy. Their time-integrated bolometric radiation amounts to 10^{49.5 ± 0.5} erg; similar energies are radiated by old SN shells. Most of the matter is ejected at speeds near 10^{8.8 ± 0.3} cm s^-1.

If supernovae are eventually propelled by pair plasma, pressure balance forces their shells into small-filling-factor fragments, or filaments. Such filamentary shells have a high photon-storage capacity. Once they are transparent in the continuum, they are still highly opaque near all the resonances. Photon leakage via diffusion can give rise to an exponentially declining light curve. The ‘photospheric’ and ‘nebular’ stage can thus be understood as the stages in which the shell is opaque and transparent in the continuum, respectively.

The universal powering of the exponential tails by radioactive decay is not without problems. The different SN types can perhaps be explained by hydrogen or helium stars exploding as red or blue supergiants. A radio flare can only be observed when the progenitor star’s late windzone is sufficiently transparent.