BVRI PHOTOMETRY OF SN-1993J IN M81 .1. PERIOD APRIL 01-30 1993

We present BVRI photometry of supernova SN 1993J in Messier 81 for the period of April 01-30 1993 obtained with the 105-cm Schmidt telescope of Kiso Observatory. The magnitudes were determined through a compari son with two nearby reference stars. The estimated accuracy of the dat a is +/-0.02 mag. We also present an R-band pre-discovery image taken on March 25.6 (UT), 2.7 d before the first detection, from which we de rive a (conservative) upper limit of 18.5 for SN 1993J. The supernova' s light curve is unique, as it shows neither a typical plateau nor a l inear decline, which suggests that it constitutes a new subclass of Ty pe II supernova and that its progenitor was not a typical red supergia nt.