1998NewA....3..125S

We describe three optical spectra and four photometric observations of SN1987C. The light curve is best described by a Type II-P template. The first spectrum of SN1987C, at day 53, is similar to spectra of other members of the "Type IIn" subclass. Spectra at 80 and 231 days appear essentially identical to late-time spectra of normal Type II-P supernovae. The data provide clues to suggest that at least this example of a "IIn" object was a hidden Type II-P supernova during its early evolution. We believe that we have observed the effects of a transition from emission dominated by the kinetic energy of an expanding shell to emission dominated by the radioactive decay of synthesized isotopes. As far as we know, this is the first time such a transition has been observed.