TITLE:   GCN CIRCULAR
NUMBER:  8973
SUBJECT: GRB 090309: Swift/UVOT Upper Limits
DATE:    09/03/10 22:03:58 GMT
FROM:    Wayne Landsman at GSFC/SSAI  <wayne.b.landsman@nasa.gov>

W.B. Landsman (NASA/GSFC) and P. Evans (U. Leicester) report on behalf 
of the Swift/UVOT team:

The Swift/UVOT observed the field of GRB 090309 starting 82 s after the 
BAT trigger (Evans et al., GCN Circ. 8964). No optical afterglow is 
detected in the initial UVOT exposures at the refined position of the 
X-ray afterglow (Goad et al., GCN Circ. 8969).     An r~19  field star ( 
GSC S9QR039837) is detected 3" from the XRT position.      Three-sigma 
upper limits using the UVOT photometric system (Poole et al. 2008, 
MNRAS, 383, 627) in a 2" radius aperture for the first finding chart 
(FC) exposure and subsequent exposures are:

Filter          T_start(s)   T_stop(s)      Exp(s)       Mag

white (FC)          82          231          147         >21.0
white               82         6136          564         >21.8
v                  624        17530         1317         >20.7
b                  549        23995         1088         >21.4
u                  294        23315         2241         >21.5
uvw1               673        22401         1998         >21.6
uvm2               648        18210         1875         >21.6
uvw2               599        16617         1318         >21.6

The values quoted above are not corrected for the Galactic extinction 
due to the reddening of E(B-V) = 0.23 in the direction of the burst  
(Schlegel et al. 1998).