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S. Jha, P. M. Garnavich, P. M. Challis, R. P. Kirshner (Harvard-Smithsonian Center for Astrophysics), A. G. Riess, A. V. Filippenko, W. Li, M. Modjaz, R. R. Treffers (University of California, Berkeley), E. K. Grebel (University of California, Santa Cruz), P. Seitzer (University of Michigan), G. H. Jacoby (Kitt Peak National Observatory), P. J. Benson (Wellesley College), A. Rizvi, L. A. Marschall (Gettysburg College)
We present extensive early-time photometric and spectroscopic observations of the type-Ia SN 1998bu in the Leo I Group galaxy M96 (NGC 3368). The well-sampled optical light curves consist of 311 UBVRI observations obtained from several telescopes: the F. L. Whipple Observatory 1.2-m, the MDM Observatory 2.4-m, the WIYN Observatory 3.5-m, the Kitt Peak National Observatory 0.9-m, the Whitin Observatory 0.6-m at Wellesley College, the Gettysburg College Observatory 0.4-m and the 0.76-m Katzman Automatic Imaging Telescope operated by UC Berkeley. The supernova reached maximum brightness in the B band on JD 2450952.8 ± 0.8, with B = 12.22 ± 0.03 and V = 11.88 ± 0.02. There is strong evidence for considerable interstellar extinction along the line of sight to the supernova, but the light curve is otherwise quite typical of type-Ia supernovae (SNe Ia). The distance to M96 has been measured via HST observations of Cepheids in the galaxy (Tanvir et al. 1995), making SN 1998bu very useful in determining the absolute luminosity of SNe Ia. We combine these observations with those of other Cepheid-calibrated SNe Ia and SNe Ia in the Hubble flow and perform a Multicolor Light Curve Shape analysis to derive a Hubble Constant of 64 ± 4 km/s/Mpc (internal error), but subject to several sources of systematic uncertainty in the Cepheid distance scale.
The author(s) of this abstract have provided an email address for comments about the abstract: sjha@cfa.harvard.edu