THE LOW-VELOCITY, RAPIDLY FADING TYPE Ia SUPERNOVA 2002es

SN 2002es is a peculiar subluminous Type Ia supernova (SN Ia) with a combination of observed characteristics never before seen in an SN Ia. Photometrically, SN 2002es differs from both SN 1991bg-like and SN 2002cx-like supernovae. Although at maximum light it is subluminous (M sub(B) = -17.78 mag), SN 2002es has a relatively broad light curve ( Delta m sub(15)(B) = 1.28 + or - 0.04 mag), making it a significant outlier in the light-curve width versus luminosity relationship. We estimate a super(56)Ni mass of 0.17 + or - 0.05 M sub([middot in circle]) synthesized in the explosion, relatively low for an SN Ia. We also present a less extensive data set for SN 1999bh, an object which shares similar photometric and spectroscopic properties. Both objects were found as part of the Lick Observatory Supernova Search, allowing us to estimate that these objects should account for 2.5% of SNe Ia within a fixed volume. Current theoretical models are unable to explain the observed characteristics of SN 2002es.