TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3538 SUBJECT: GRB050607: refined analysis of prompt REM observations DATE: 05/06/08 12:42:48 GMT FROM: Vincenzo Testa at INAF/Astro. Obs. of Rome V. Testa, E. Palazzi, P. D'Avanzo, L.A. Antonelli, E. Molinari, D. Fugazza, S. Covino, S. Campana, F.M. Zerbi, G. Chincarini, M. Rodono', G. Tosti, P. Conconi, G. Cutispoto, L. Nicastro, F. Vitali, E. Meurs, P. Goldoni, on behalf of the REM/ROSS Team We refined the analysis of the field of GRB050607 observed with the REM telescope (GCN 3523) in fully automated mode simultaneously in the near infrared and in the optical. Two R-band 3s exposures and five H-band 10s exposures have been re-analyzed to search for new objects at the positions reported by Rhoads (GCN 3527) and Pagani et al. (GCN 3528). We confirm the non-detection reported in GCN 3523 and derived upper limits at 3 sigma level (see the table below). The UT differences between optical and IR acquisitions are due to different overheads and observing strategies adopted by the two instruments. Filter Instrument UT t_exp Time_from_burst Mag. Upper Limit -------------------------------------------------------------------------- R ROSS 09:14:49 6s 207s 17.1 H REMIR 09:14:34 50s 192s 16.0 Observations were performed under moderate seeing conditions, the La Silla DIMM giving an instantaneous value of 1.5 arcsec, and in photometric conditions. Magnitudes have been calibrated with a set of stars around the position of the optical detection (GCN 3527) extracted from the 2MASS catalog for the H filter and from the USNO B1.0 catalog for the R filter. This message may be cited.