THE NEBULAR PHASE SPECTRA OF SN1993J

From June 19 to August 27, using the 2.16 m telescope in the Beijing A stronomical Observatory, we obtained some low resolution spectra of SN 1993J. The forbidden emission lines [O I], [Ca II] were very strong an d dominated the spectra. However, the Halpha and He lines were very we ak. Many fine structures appeared in the Halpha and [OI] lines. We fou nd that the supernova had entered the nebular phase and strong instabi lity and chemical mixing had occurred in the ejecta.