TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1458 SUBJECT: GRB 020405: HST observations reveal red bump DATE: 02/07/23 07:15:10 GMT FROM: Paul Price at RSAA, ANU P.A. Price (RSAA, ANU), S.R. Kulkarni, D.W. Fox and J.S. Bloom (Caltech) report on behalf of the larger Caltech-NRAO-CARA GRB collaboration: We observed the afterglow of GRB 020405 (GCN #1326) with HST+WFPC2 at several epochs spanning 19-31 days after the GRB in F555W, F702W and F814W, with additional observations approximately two months after the GRB to remove host contamination. These observations formed part of our large Cycle 10 program to search for SNe underlying low redshift GRBs. We have performed Novicki-Tonry photometry (see astro-ph/0207187) on both ground-based and HST imaging. The resultant light curve, including data from Bersier et al. (astro-ph/0206465), is at http://www.mso.anu.edu.au/~pap/grb020405/ . An excess of flux is evident in the HST images, compared to an extrapolation of the light-curve from early times. Based on the red colour and the time of peak emission, we identify this excess as a SN associated with GRB 020405. We have plotted the light-curve of SN 1998bw at z=0.695 (Masetti et al., GCN #1330) and dimmed by 0.5 mag as a comparison. This SN appears to be red relative to SN 1998bw, but this is sensitive to the amount of flux in the afterglow at the final available HST images. Further HST observations to measure the host galaxy and remove this ambiguity are planned for August. This message may be cited.