Optical Photometry and Spectroscopy of the SN 1998bw–like Type Ic Supernova 2002ap

We present optical photometric and spectral data of the peculiar Type Ic SN2002ap. Photometric coverage includes UBVRI bands from 2002 January 30, the dayafter discovery, through 2002 December 12. There are 5 early-time spectra and 8in the nebular phase. We determine that SN 2002ap is similar to SN 1997ef andthe GRB-associated SN 1998bw with respect to spectral and photometriccharacteristics. The nebular spectra of SN 2002ap present the largest Mg I]\lambda 4571 to [O I] \lambda \lambda 6300, 6364 ratio of any supernova spectrayet published, suggesting that the progenitor of SN 2002ap was a highlystripped star. Comparing the nebular spectra of SN 1985F and SN 2002ap, wenotice several similar features, casting the classification of SN 1985F as anormal Type Ib supernova in doubt. We also present nebular modeling of SN2002ap and find that the object ejected >~ 1.5 M_{sun} of material within theouter velocity shell of the nebula (~5500 km/s) and synthesized ~0.09 M_{sun}of 56Ni.Comment: 45 pages, accepted for publication in the October 2003 issue of PASP. Some references adde