TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3046
SUBJECT: GRB050219b: No Swift UVOT Detection of Afterglow Emission
DATE:    05/02/20 04:45:45 GMT
FROM:    Patricia Schady at MSSL/Swift  <ps@mssl.ucl.ac.uk>

M. Ivanushkina (PSU), 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) P. Broos (PSU), T. Kennedy, P. Smith, B. Hancock (MSSL), S. Koch 
(PSU), M. Carter, H. Huckle (MSSL),  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:

Filter	Lim_Mag  Duration   T_start
  UVW2	~ 22.04	  1154	     T+3120
  UVM2	~ 20.95   100	     T+3243
  UVW1	~ 20.65   100	     T+3349
  U	~ 20.92   100	     T+3455
  B	~ 20.85   100	     T+3561
  V	~ 19.38   100	     T+3136

The limiting magnitude for the UVW2 filter was calculated from a summation 
of four separate exposures taken at different times between observations 
made in other filters. This is the cause of the overlap between the 
duration of the UVW2 exposure and the start of some of the other 
exposures.

We caution that the instrument is not yet fully calibrated and that the
magnitude limits presented here may need to be refined.