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E. Labbe, G. Galaz (PUC), K. Krisciunas, N. Suntzeff, J. Espinoza, D. Gonzalez (CTIO), M. M. Phillips, M. Roth (LCO), L. Germany (ESO)
We present the most complete infrared (JHK) and optical (BVRI) light curves ever obtained of a Type Ia Supernova: SN 1999ac. The SN ocurred in the outer part of the Sc galaxy NGC 6063. It was discovered two weeks before maximum light, and observations were begun shortly thereafter. We present 39 nights of optical photometry spanning 144 days, plus 33 nights of infrared photometry spanning 93 days. Spectroscopically, SN 1999ac closely resembled SN 1991T in displaying a spectrum dominated by strong Fe III absorption ~ 2 weeks before maximum light. However, by maximum the spectrum of SN 1999ac was essentially ``normal'', and in this sense resembled more the ``peculiar''SN 1999aa. Following the methods of Phillips et al. (1999) and Krisciunas et al. (2000) we derive a total extinction towards this object of AV = 0.51 mag, although it is not clear that these methods can be applied to 91T/99aa-like events. From the measured radial velocity of the host galaxy, corrected for our motion with respect to the Local Group and the microwave background, we obtain MV ~ -19.7 assuming H0 = 65 km/sec/Mpc. Combining the optical and IR photometry, we produce the best bolometric light curve to date of a 91T/99aa-like event. This research is supported in part by the CTIO REU/PIA Program, which is funded by the National Science Foundation.