Optical and infrared photometry of the Type Ia supernovae 1999da, 1999dk, 1999gp, 2000bk, and 2000ce

We present BV RI photometry of the Type Ia supernovae 1999da, 1999dk, 1999g p, 2000bk, and 2000ce, plus infrared photometry of three of these. These ob jects exhibit the full range of decline rates of Type Ia supernovae. Combin ed optical and infrared data show that families of V-infrared color curves can be used to derive the host extinction (A(V)) of these objects. Existing data do not yet allow us to construct these loci for all color indices and supernova decline rates, but the V-K color evolution is sufficiently unifo rm that it allows the determination of host extinction over a wide range of supernova decline rates to an accuracy of roughly +/-0.1 mag. We introduce a new empirical parameter, the mean I-band flux 20 to 40 days after maximu m light, and show how it is directly related to the decline rate.