We present photometry of the transient associated with GRB 030329 obtained with the CTIO 1.3–meter telescope and the ANDICAM instrument , a dual optical/infrared imager with a dichroic centered at one micron .
Without the need for light curve interpolation to produce snapshot broadband spectra , we show that the transient spectrum remained statistically achromatic from day 2.7 to day 5.6 , during a re-brightening episode .
Associating the light in these early epochs with the GRB afterglow , we infer a modest level of extinction due to the host galaxy in the line–of–sight toward the GRB : A _ { V } ( host ) = 0.30 \pm 0.03 mag for \beta = -0.5 and A _ { V } ( host ) < 0.4 mag ( 3 \sigma ) for any physically plausible value of \beta ( with flux f _ { \nu } \propto \lambda ^ { - \beta } ) .
We conclude that the spectral slope of the afterglow component was more than \beta = - 0.8 between day 2.7–5.6 after the GRB , excluding the possibility that the synchrotron cooling break passed through the optical/IR bandpass over that period .
Taking extinction into account , a decomposition of the light curve into an afterglow and supernova component requires the presence of a supernova similar to that of SN 1998bw , an afterglow that shows some evidence for a second break around day 8–10 , and a fifth re-brightening event around day 15 .
Assuming an SN 1988bw-like evolution and a contemporaneous GRB and SN event , the peak SN brightness was M _ { V } = ( -19.8 \pm 0.4 ) -5 \log _ { 10 } h _ { 65 } mag .