GALEX Spectroscopy of SN 2005ay suggests a UV spectral uniformity among type II-P supernovae

摘要

We present the first results from our GALEX program designed to obtainultraviolet (UV) spectroscopy of nearby core-collapse supernovae (SNe). Ourfirst target, SN 2005ay in the nearby galaxy NGC 3938, is a typical member ofthe II-P SN subclass. Our spectra show remarkable similarity to those of theprototypical type II-P event SN 1999em, and resemble also Swift observations ofthe recent type II-P event SN 2005cs. Taken together, the observations of thesethree events trace the UV spectral evolution of SNe II-P during the first monthafter explosion, as required in order to interpret optical observations ofhigh-redshift SNe II-P, and to derive cross-filter K-corrections. While stillhighly preliminary, the apparent UV homogeneity of SNe II-P bodes well for theuse of these events as cosmological probes at high redshift.