Non-equilibrium radiative transfer in supernova theory : models of linear type II supernovae.

We present hydrodynamic computations of light curves of linear type II supernovae (SNe II-L) accounting for multi-frequency- group time- dependent radiation transfer. We briefly discuss the computation method which involves implicit hydrodynamics coupled to radiation. The equation of state and the absorption coefficient including the Lyman jump describe ionization balance without the assumption of equilibrium between matter and radiation. Our set of hydrodynamical models shows that the observations of weak SNe II-L are well described by the explosion of a supergiant presupernova with a radius ∼600 R_sun and with a small hydrogen envelope mass ∼ 1 - 2 M_sun. We pay special attention to the exceptionally bright Supernova 1979C. A red supergiant presupernova with larger radius ∼6000 R_sun satisfactorily reproduces the light curve of SN 1979C with the standard explosion energy of about (1 - 2) × 1O⁵¹ ergs and with the same small hydrogen envelope mass. The unusual brightness is naturally explained by reradiation of ultraviolet photons, created at shock breakout, in the superwind shell surrounding the exploding star, if we assume the same parameters for the superwind as derived from the radio observations of this supernova. Both weak and brightest SN II-L events are explained without involving large amounts of radioactive material. We conclude that all type II supernovae (linear, plateau and 1987A subtypes) are probably produced by one and the same explosion mechanism and all varieties in their observational appearance are completely explained by the presupernova radius, by the power of the presupernova wind and by the amount of hydrogen left in the envelope.