SN 1987A in the LMC. II - Optical photometry at Cerro Tololo

We present optical UBV(RI)_KC_ photometry of SN 1987A in the Large Magellanic Cloud for days 188-477 since core collapse. The luminosity evolution has been remarkably exponential over this time period. There are large systematic differences of up to 0.3 mag between the CTIO photometry and other published photometry due to the presence of strong emission lines during this exponential-decline phase. We have constructed a bolometric light curve based on optical and infrared data. The bolometric luminosity has declined with an e-folding time of 100.5 days, roughly consistent with the e-folding time of 111.3 days for the radioactive decay of ^56^Co. Discrepancies of up to 0.2 mag in the bolometric magnitude are due to differences in the various photometric datasets and interpolation schemes. By day 350, the rate of decline of the bolometric light curve had increased appreciably, consistent both with the predictions of models of gamma-ray leakage from the supernova photosphere and the observations of gamma rays.