GCN Circular 9859

P. Schady (MSSL-UCL) reports on behalf of the Swift/UVOT team.

The Swift/UVOT began settled observations of the field of GRB 090831C 121s 
after the BAT trigger (Schady et al., GCN Circ 9854). No new source is 
detected within the XRT error circle (Evans et al., GCN Circ 9855) in any 
of the individual or combined UVOT filters.

The 3-sigma upper limits of detecting a source at the position of the 
X-ray afterglow in the first white band finding chart (fc) observation and 
in consecutive coadded observations for each of the UVOT filters are as 
follows:

Filter	T_start(s) T_stop(s) Exp(s) Mag 3-sig UL
wh (fc)    121       270     147      > 20.78
wh         561       1183    206      > 20.73
vv         610       1060    58       > 18.47
bb         536       1159    58       > 19.30
uu         279       1134    285      > 19.95
w1         660       1109    58       > 18.74
m2         635       1084    58       > 18.48
w2         586       1209    78       > 18.95


The values quoted above are not corrected for the Galactic extinction due 
to the large reddening of E(B-V) = 0.38 in the direction of the burst 
(Schlegel et al., 1998). The photometry is on the UVOT photometric system 
described in Poole et al. (2008, MNRAS, 383, 627).