TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1375 SUBJECT: GRB020405: VLT observations of the OT environment DATE: 02/04/18 14:18:16 GMT FROM: Nicola Masetti at ITeSRE,CNR,Bologna N. Masetti, E. Palazzi (IASF/CNR, Bologna), E. Maiorano, A. Simoncelli (U. Bologna), E. Pian (INAF, OA Trieste), A. Castro-Tirado (IAA-CSIC, Granada), A. Fruchter (STScI, Baltimore), J. Greiner (MPE Garching and AI Potsdam), J. Hjorth (U. Copenhagen), L. Kaper, E. van den Heuvel (U. Amsterdam), R. Cabanac, A. Kaufer (ESO), on behalf of the GRACE Collaboration, report: "We have obtained an R-band image (2 x 3 minutes integration) of GRB020405 from VLT-UT3 (Melipal) plus FORS1 on 2002 Apr. 15.244 under a seeing of 0.65 arcsec. We find that the OT is located within a complex environment composed of at least four extended objects, one of which is underlying the OT and showing a bright knot (possibly a star-forming region, or alternatively the host nucleus) ~1 arcsec south of the OT itself. Also, the presumed host galaxy indicated by Hjorth et al. (GCN #1329) and located ~2 arcsec southwest of the OT seems not to be the actual host but a galaxy which is likely interacting with it. Indeed, a spectrum of this galaxy taken with Melipal+FORS1 on 2002 April 7.310 shows that it is at the same redshift of the OT (GCNs #1330, #1340). This finding strengthens the suggestion that GRBs are sometimes associated with interacting galaxies possibly displaying substantial star formation, as seen e.g. for GRB001007 (Castro Ceron et al. 2002, A&A, in press [astro-ph/0110049]). No suggestion of a break in the light curve (see GCN #1369) is apparent up to ~10 days after the GRB. However, in the VLT image reported above, the OT brightness is already substantially contamined by the host emission. For this reason it would be quite difficult to see any future possible break in the OT light curve with ground-based observations. A close-up of the VLT R-band field around the OT can be found at: http://tonno.tesre.bo.cnr.it/~masetti/grb020405.html This message can be cited.".