GALEX Spectroscopy of SN 2005ay Suggests Ultraviolet Spectral Uniformity among Type II-P Supernovae
Smith, G. P.; Gal-Yam, A.; Kirshner, R. P.; Filippenko, A. V.; Foley, R. J.; Baron, E.; Maoz, D.; Turatto, M.; Cappellaro, E.; Benetti, S.; Fox, D. B.; Bufano, F.; Mazzali, P. A.; Nomoto, K.; Simon, J. D.; Ellis, R. S.; Ofek, E. O.; Li, W.; Leonard, D. C.; Matheson, T.; Zampieri, L.; Modjaz, M.; Van Dyk, S. D.; Hicken, M.; Barlow, T. A.; Small, T. A.; Challis, P. J.
Israel, United States, Italy, Germany, Japan, United Kingdom
Abstract
We present the initial results from our GALEX program designed to obtain ultraviolet (UV) spectra of nearby core-collapse supernovae (SNe). Our first target, SN 2005ay in the nearby galaxy NGC 3938, is a typical member of the SN II-P subclass. Our spectra show remarkable similarity to those of the prototypical Type II-P SN 1999em, and resemble also Swift observations of the recent Type II-P SN 2005cs. Taken together, the observations of these three events trace the UV spectral evolution of SNe II-P during the first month after explosion, as required in order to interpret optical observations of high-redshift SNe II-P, and to derive cross-filter K-corrections. While still highly preliminary, the apparent UV homogeneity of SNe II-P bodes well for the use of these events as cosmological probes at high redshift.