ON THE RELATIVE FREQUENCIES OF SPECTROSCOPICALLY NORMAL AND PECULIAR TYPE-IA SUPERNOVAE

After defining what we mean by spectroscopically ''normal'' and ''pecu liar'' Type la supernovae, we report the results of an attempt to subc lassify 84 SNe Ia either as normal or as like one of the recent, pecul iar SNe Ia: 1991T, 1991bg, or 1986G. Only SNe 1957A and 1960H are foun d to have been certifiably abnormal, with SN 1957A appearing to have b een like SN 1991bg, and SN 1960H having been like SN 1991bg or SN 1986 G; SNe 1971I and 19801 are under suspicion of having been like SN 1986 G, and SN 1988G of having been like SN 1991T. Of the SNe la we have be en able to classify either as normal or as peculiar, 89% (or 83%, coun ting those under suspicion as peculiar) are normal. Our main conclusio n is that the observational sample of SNe la is strongly peaked at ''s pectroscopically normal.'' We further conclude that when arranged in t he photometric sequence of Phillips [ApJ, 413, L105 (1993)] SNe Ia als o form a spectroscopic sequence, and that peculiar SNe Ia are over-rep resented in the Phillips sample.