TITLE:   GCN CIRCULAR
NUMBER:  9203
SUBJECT: GRB 090422: Swift/UVOT Upper Limits
DATE:    09/04/23 11:37:54 GMT
FROM:    Alice Breeveld at MSSL-UCL  <aab@mssl.ucl.ac.uk>

A. A. Breeveld (MSSL/UCL) and T. N. Ukwatta (GSFC/GWU) report on  
behalf of the Swift UVOT team:

     The Swift/UVOT observed the field of GRB 090422 starting 55 s  
after the BAT trigger (Ukwatta, et al., 2009, GCN Circ. 9185). Settled  
exposures started at T+74 s with a Finding Chart (FC) in the white  
filter. We do not find any new source, at the enhanced position of the  
XRT afterglow (Beardmore, et al. 2009, GCN Circ. 9194) nor at the  
position of the candidate found by the Liverpool Telescope (Guidorzi,  
et al. 2009, GCN Circ. 9197).  3-sigma upper limits for detecting a  
source in the white and u FCs, and subsequent co-added images in all  
filters are:

Filter           T_start   T_stop   Exp(s)      Mag
----------------------------------------------------------
white (FC)  74           224       147         >20.5
u (FC)          287        537        246        >19.6		

v                  617         11744   1317      >20.3
b                  542         18318   1145     >20.8
u                  690         24099   2059     >20.8
uvw1          666          23300   2203     >21.0
uvm2          641          22393   2092     >20.8
uvw2          592          10831   1318     >20.8
white          566          5591     341.4    >20.8
---------------------------------------------------------

The quoted upper limits have not been corrected for the expected  
Galactic extinction along the line of sight corresponding to a  
reddening of E_{B-V} = 0.198 mag (Schlegel, et al., 1998, ApJS, 500,  
525).  All photometry is on the UVOT photometry system described in  
Poole et al. (2008, MNRAS, 383, 627).