TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3050 SUBJECT: GRB050219b: No Swift UVOT Detection of Afterglow Emission DATE: 05/02/20 19:06:55 GMT FROM: Patricia Schady at MSSL/Swift T. Poole (MSSL), C. Gronwall (PSU), A. Blustin (MSSL), P. Brown (PSU), S. Rosen, K. McGowan, M. De Pasquale (MSSL), P. Boyd (GSFC/UMBC), S. Holland, M. Still (GSFC/USRA), W. Landsman (GSFC), S. Hunsberger (PSU), A. Breeveld (MSSL), P. Roming (PSU), K. Mason, P. Schady (MSSL), M. Ivanushkina (PSU), T. Kennedy, P. Smith, B. Hancock (MSSL), S. Koch (PSU), M. Carter, H. Huckle (MSSL), P. Broos, J. Racusin (PSU), E. Fenimore (LANL), B. Zhang (UNLV), J. Nousek (PSU), N. Gehrels (GSFC), on behalf of the Swift UVOT team. The Swift Ultra-Violet/Optical Telescope (UVOT) began observations of GRB050219b on February 19, 2005, at 12:57:51 UT, 52 minutes after the initial Swift BAT trigger (Cummings et al, GCN 3044). The delay in observations was due to the Earth-limb constraint, which prevented an immediate slew. We detect no source at the Swift XRT position (Burrows et al, GCN 3043). The limiting magnitudes (3-sigma) in each of the UVOT filters are as follows: A re-examination of the UVOT data at the new XRT position (Racusin et al, GCN 3049) revealed no new source detection down to the following 3-sigma limiting magnitudes Filter Lim_Mag Duration T_start UVW2 ~ 22.16 1154 T+3120 UVM2 ~ 22.24 1435 T+3243 UVW1 ~ 22.23 940 T+3349 U ~ 20.74 100 T+3455 B ~ 20.9 100 T+3561 V ~ 19.41 100 T+3136 Several exposures were taken in the UV filters, and these were co-added in order to derive the limiting magnitudes. This is the cause of the apparent overlap between the duration of these exposure and the start time of the exposures in the optical filters. We caution that the instrument is not yet fully calibrated and that the magnitude limits presented here may need to be refined.