Explosion Energies, Nickel Masses, and Distances of Supernovae of Type IIP

Abstract

The hydrodynamical modelling of Type II plateau supernova light curves predicts a correlation between three observable parameters (the plateau duration, the absolute magnitude and photospheric velocity at the middle of the plateau) on the one side and three physical parameters (the explosion energy E, the mass of the envelope expelled M, and the presupernova radius R) on the other side. The correlation is used, together with adopted EPM distances, to estimate E, M, and R for a dozen of well-observed SNe IIP. For this set of supernovae, the resulting value of E varies within a factor of 6 [0.5< E/(10^51 erg)<3], whereas the envelope mass remains within the limits 10< M/M_sun <30. The presupernova radius is typically (200-600)R_sun, but can exceed 1000R_sun for the brightest supernovae (e.g., SN 1992am). A new method of determining the distance of SNe IIP is proposed. It is based on the assumption of a correlation between the explosion energy E and the Ni56 mass required to power the post-plateau light curve tail through Co56 decay. The method is useful for SNe IIP with well-observed bolometric light curves both during the plateau and radioactive tail phases. The resulting distances and future improvements are discussed.