TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4567
SUBJECT: GRB 060121: Swift/UVOT upper limits
DATE:    06/01/23 17:00:25 GMT
FROM:    Alice Breeveld at MSSL-UCL  <aad@mssl.ucl.ac.uk>

A. A. Breeveld (UCL-MSSL), L. Angelini (GSFC), D. Hinshaw (GSFC-SPSYS), 
M. Carter (UCL-MSSL), N. Gehrels (GSFC) on behalf of the Swift/UVOT 
team

The Swift UVOT instrument began observing the HETE-discovered GRB 
050121 (Arimoto et al., GCN 4550; Prigozhin et al., GCN 4551) as a 
target of opportunity at 01:21:28 UT on 22 January 2006 10.6 ks after 
the burst. No new source is found at the XRT position (Mangano et al., 
GCN 4565) in coadded images from the first ToO observation, with any of 
the filters used down to the following 5-sigma magnitude upper limits. 
No exposures were taken in UVW1 or UVM2. These values are not corrected 
for Galactic extinction.

Filter	     T_range(s)          Exp(s)    5sigUL(mag)
B	     10593-16768     1099      20.6
V            11917-12639      712      19.4
U            21650-22022      368      19.7
UVW2   11003-18423      1625     21.2
White    10798-17682      1099     20.7