TITLE: GCN GRB OBSERVATION REPORT NUMBER: 617 SUBJECT: GRB 000307 optical observations DATE: 00/03/26 11:39:58 GMT FROM: Holger Pedersen at Copenhagen U Obs H. Pedersen, B. L. Jensen (University of Copenhagen), J. Gorosabel (Danish Space Research Institute, Copenhagen), J. P. U. Fynbo (Aarhus University) report on behalf of a wider, European group: We have observed the entire error box of GRB 000307 (cf. Hurley et al., GCN #601), using the WFI instrument attached to the 2.2-m ESO/MPI telescope at La Silla. The exposure dates were: 2000 March 10.015 UT, 2 * 600 s R-band, seeing 0.9" - 1.2" 2000 March 23.019 UT, 3 * 600 s R-band, seeing 1.1" - 1.6" The two exposure sets were compared, using image blinking. The closeness of Betelgeuse implies scattered light across the error box, and hence a non-uniform limiting magnitude. Using the standard stars provided by Henden et al. (GCN #608) we estimate that most of the error box has been searched to magnitude R ~22.0. No candidate counterpart was found. We acknowledge the assistance of the La Silla staff. Observations were carried out at the European Southern Observatory under programme 64.H-0573(A).