Optical-Infrared ANDICAM Observations of the Transient Associated with GRB 030329

We present photometry of the transient associated with GRB 030329 obtainedwith the CTIO 1.3--meter telescope and the ANDICAM instrument, a dualoptical/infrared imager with a dichroic centered at one micron. Without theneed for light curve interpolation to produce snapshot broadband spectra, weshow that the transient spectrum remained statistically achromatic from day 2.7to day 5.6, during a re-brightening episode. Associating the light in theseearly epochs with the GRB afterglow, we infer a modest level of extinction dueto the host galaxy in the line--of--sight toward the GRB: A_V(host) = 0.30 +/-0.03 mag for beta = -0.5 and A_V(host) < 0.4 mag (3 sigma) for any physicallyplausible value of beta (with flux f_nu ~ lambda^-beta). We conclude that thespectral slope of the afterglow component was more than beta = -0.8 between day2.7-5.6 after the GRB, excluding the possibility that the synchrotron coolingbreak passed through the optical/IR bandpass over that period. Takingextinction into account, a decomposition of the light curve into an afterglowand supernova component requires the presence of a supernova similar to that ofSN 1998bw, an afterglow that shows some evidence for a second break around day8-10, and a fifth re-brightening event around day 15. Assuming an SN1988bw-like evolution and a contemporaneous GRB and SN event, the peak SNbrightness was M_V = -19.8 +/- 0.4 - 5 log h_65 mag.