TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4373
SUBJECT: GRB 051221: Swift/UVOT upper limits
DATE:    05/12/21 16:53:16 GMT
FROM:    Alice Breeveld at MSSL-UCL  <aad@mssl.ucl.ac.uk>

A. A. Breeveld (UCL-MSSL), F. Marshall (GSFC), A. Parsons (GSFC), P. 
Mezsaros (PSU), M. Chester (PSU) on behalf of the Swift/UVOT team

The Swift/UVOT began the settling exposure of the field of GRB 051221 at 
01:52:29 on 2005-12-21, 73s after the BAT trigger (Parsons et al. GCN 
4363). The 86s delay reported in GCN 4363 did not include the settling 
exposure. No source was detected at the XRT position (Burrows et al. GCN 
4366) nor the candidate IR position (Bloom, GCN 4368) down to the 
following 5-sigma upper limits. No correction has been made for the 
expected visual extinction of about 0.23 magnitudes.

  Filter  T_range(s)   Summed exposure times  5sigUL(mag)
  V       73 - 12530   1109                   19.2
  B       453 - 19212  2098                   20.8
  U       399 - 18305  2098                   20.2
  W1      345 - 14127  1080                   20.3
  M2      290 - 13437  1298                   20.7
  W2      562 - 8341   1119                   20.7
  white   507 - 934    99.5                   19.2