Spectroscopic and photometric observations of SN 1987A : the first 50days.

Spectroscopic and photometric observations of SN 1987a in the LMC, obtained with the 1.9-m SAAO telescope at Cape Town, are presented. In the first 7-8 days after maximum light, the photometric and spectroscopic characteristics were found to change unusually rapidly for a type II supernova. The unusual reddening rate for B-V and U-B colors may be due to the early appearance and growth of unusually strong, presumably metallic, absoption lines in the blue and ultraviolet parts of the spectrum. The high velocities noted in the hydrogen lines and the rapid apparent deceleration suggest that the initial shock energy went mostly into kinetic energy in a low-mass shell. Data indicate that the maximum H-alpha absorption occurs at the highest levels in the atmosphere and that the other hydrogen lines come from successively lower levels, with the photosphere as the limit.