Strong effects of time-dependent ionization in early SN 1987A

We study time-dependent hydrogen ionization in the atmosphere of SN 1987A during the first month after the supernova explosion. The model includes kinetics of hydrogen ionization and excitation, molecular hydrogen kinetics, and a time-dependent energy balance. The primary strong effect of the time-dependent ionization is the enhanced hydrogen ionization compared to the steady-state model. The time-dependent ionization provides a sufficient population of excited hydrogen levels to account for the observed H alpha without invoking the external Ni-56. We find that the Ba II 6142 angstrom line in SN 1987A can be reproduced for the LMC barium abundance. This resolves the long-standing problem of the unacceptably high barium overabundance in SN 1987A. The key missing factor responsible for the barium problem is the time-dependent ionization. The modelling of the H alpha profile on day 4.64 indicates the ratio of the kinetic energy to the ejected mass approximate to 0.83x10(50) erg M-circle dot(-1).