The J-band light curve of SN 20031w, associated with GRB 031203

At z = 0.1055, the gamma-ray burst GRB 031203 is the second nearest GRB known. Using observations from the Very Large Array and the Chandra X-Ray Observatory, we derive subarcsecond localizations of the radio and X-ray afterglow of this GRB. We present near-infrared observations of the supernova SN 2003lw, which exploded in the host galaxy of GRB 031203. Our deep high-resolution Magellan data establish that this SN is spatially coincident with the radio and X-ray localizations of the afterglow of GRB 031203 to subarcsecond precision and is thus firmly associated with the GRB. We use image differencing to subtract the bright emission from the host galaxy and measure the SN flux at ∼5, ∼7, and ∼50 days after the GRB. Our J-band measurements are inconsistent with predictions derived by placing SN 1998bw (associated with GRB 980425) at z = 0.1055. In particular, our early data points show that before peak, SN 2003lw was significantly fainter in rest frame ∼1.13 μm (observed J band) than SN 1998bw. We measure similar fluxes at ∼7 and ∼50 days after the GRB, suggesting that SN 2003lw had a light-curve shape that is quite different from that of SN 1998bw, the best-studied GRB-associated SN so far.