Optical Light Curve of the Type IA Supernova 1998BU in M96 and the Supernova Calibration of the Hubble Constant

SUNTZEFF, N.; PHILLIPS, R.; COVARRUBIAS, R.; NAVARRETE, M.; PEREZ, J.J.; GUERRA, A.; ACEVEDO, M.T.; DOYLE, L.; HARRISON, TH.; KANE, S.; LONG, K.S.; MAZA, J.; MILLER, S.; PIATTI, ANDRÉS E.; + 3 COAUTORES

ASTRONOMICAL JOURNAL

Año: 1999 vol. 117 p. 1175 - 1184

0004-6256

We present the UBV(RI)_KC light curves of the Type Ia supernova SN 1998bu, which appeared in the nearby galaxy M96 (NGC 3368). M96 is a spiral galaxy in the Leo I group that has a Cepheid-based distance. Our photometry allows us to calculate the absolute magnitude and reddening of this supernova. These data, when combined with measurements of the four other well-observed supernovae with Cepheid-based distances, allow us to calculate the Hubble constant with respect to the Hubble flow defined by the distant Calán/Tololo Type Ia sample. We find a Hubble constant of 63.9+/-2.2(internal)+/-3.5(external) km s^-1 Mpc^-1, consistent with most previous estimates based on Type Ia supernovae. We note that the two well-observed Type Ia supernovae in Fornax, if placed at the Cepheid distance to the possible Fornax spiral NGC 1365, are apparently too faint with respect to the Calán/Tololo sample calibrated with the five Type Ia supernovae with Cepheid distances to the host galaxies.