Early optical spectroscopy of supernova 1987A

CCD spectroscopy of SN 1987A from February 24-28, 1987 is presented. Spectra with 10 A resolution and signal-to-noise ratio is excess of 200, over a range 3900 A to 9000 A, are reduced to flux relative to the continuum at 8000 A. Spectra as a function of time and nightly difference spectra are obtained. Strong and broad hydrogen Balmer P-Cygni profiles, increasing in intensity with time, and H-alpha absorption velocity decreasing from 19,000 km/s are seen. H-alpha velocity componnents up to 31,000 km/s are found on February 25 UT. The He I feature at 5400 A disappears after February 26 and Ca II at 8200 A appears strongly after February 27. Spectra as a function of angular distance from SN 1987A are also obtained, showing the adjacent nebular emission of the LMC. There is no evidence for a circumstellar shell. These data are most consistent with an unusually low envelope mass progenitor. 30 references