Evidence for energizing of H emission in type II supernovae by ejecta-wind interaction

Abstract

A simple model of H-α luminosity of type II supernova, $$(t\gt 100\enspace\text d)$$ energized by $$^{56}\text {Co}-^{56}\text Fe$$ decay, was applied lo the analysis of the observed H-α evolution. Of the six available SNell with known H-α fluxes at late times, three reveal the extra H-α flux above the radioactive model. This excess is interpreted as an effect of an energy release due to ejecta–wind interaction. Two SNeII, 1979C and 1987F, with the particularly strong H-α excess, show additional spectroscopic signatures, which can be attributed to the dense wind around supernovae. In SN 1987F the wind density parameter $$\dot M/u_\text w$$ is of the order of $$10^{17}\text {g cm}^{-1}$$ thus being high enough to provide a noticeable contribution arising from ejecta–wind interaction to the overall optical luminosity at late times ($$t\gt150\enspace\text d$$). The hard X-ray (kT ∽ 50 keV) luminosity of the outer shock wave must have been, in this case, of the order of $$10^{42}\enspace\text {erg}\enspace\text s^{-1}$$ at 150 d. The modelling of the H-α profile in SN 1987F at t = 150 d provides compelling evidence in favour of the existence of an inner radiative shock wave.