Bolometric Light Curves of Supernovae and Postexplosion Magnetic Fields

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The various effects leading to diversity in the bolometric light curves of supernovae are examined; nucleosynthesis, kinematic differences, ejected mass, degree of mixing, and configuration and intensity of the magnetic field are discussed. In Type Ia supernovae, a departure in the bolometric light curve from the full-trapping decline of 56Co can occur within the 2.5 years after the explosion, depending on the evolutionary path followed by the white dwarf (WD) during the accretion phase. If convection has developed in the WD core during the presupernova evolution, starting several thousand years before the explosion, a tangled magnetic field close to the equipartition value should have grown in the WD. Such an intense magnetic field would confine positrons where they originate from the 56Co decays and preclude a strong departure from the full-trapping decline as the supernova expands. This situation is expected to occur in C + O Chandrasekhar WDs as opposed to edge-lit detonated sub-Chandrasekhar WDs. If the preexplosion magnetic field of the WD is less intense than 105-108 G, a lack of confinement of the positrons emitted in the 56Co decay and a departure from full trapping of their energy would occur. The time at which the departure takes place can provide estimates of the original magnetic field of the WD, its configuration, and also of the mass of the supernova ejecta. In SN 1991BG, the bolometric light curve suggests an absence of a significant tangled magnetic field: its intensity is estimated to be lower than 103 G. Chandrasekhar-mass models do not reproduce the bolometric light curve of this supernova. For SN 1972E, on the contrary, there is evidence for a tangled configuration of the magnetic field and its light curve is well reproduced by a Chandrasekhar WD explosion. A comparison is made for the diagram of absolute magnitude and rate of decline in Type Ia supernovae coming from different explosion mechanisms. The effects of mixing and ejected mass in the bolometric light curve of Type Ib, Ic supernovae are also discussed.