Infrared Photometry of Supernova 1987A - the First Four Months

The results of the first 4 mo of the ESO La Silla IR photometric monitoring program of SN 1987A. IR light curves are presented, and the IR data are combined with optical photometry to determine the luminosity, the effective radius, and the effective temperature, and how they evolved. Particular attention is given to the IR excess which become apparent beginning less than 1 mo after the explosion. Three possible interpretations of the excess IR emission are presented: an IR echo from preexisting dust, thermal emission from dust that has just condensed from the ejecta, and free-free emission from the expanding ejecta. None of the models are entirely satisfactory.