TITLE:   GCN CIRCULAR
NUMBER:  9949
SUBJECT: GRB090926B: Swift/UVOT Upper Limits
DATE:    09/09/27 12:42:23 GMT
FROM:    Samantha Oates at MSSL  <sro@mssl.ucl.ac.uk>

S. R. Oates (MSSL-UCL) and D. Grupe (PSU) report on behalf of the  
Swift/UVOT team:

The Swift/UVOT began settled observations of the field of
GRB 090926B 98s after the BAT trigger (Grupe et al., GCN 9935).
We do not detect any source at the position reported by
VLT (Malesani et al., GCN 9944) and the enhanced Swift XRT
position (Grupe et al. GCN 9940).

The 3-sigma upper limits for the finding charts (FC) and summed images  
are:

Filter   T_start   T_stop   Exp(s)  Mag (3-sigma upper limit)
-------------------------------------------------------------
white(FC)  98       248	     147       > 21.02
white      591      2053     303       > 21.21
v	   641      2103     175       > 19.19
b	   567      5976     226       > 20.32
u(FC)      310      560	     246       > 20.30
u	   715      5900     333       > 20.22
uvw1	   691      5695     333       > 20.25
uvm2	   5290     5490     197       > 19.77
uvw2	   616      1389     58        > 19.09
-------------------------------------------------------------

The quoted upper limits have not been corrected for the expected
Galactic extinction along the line of sight of E_(B-V) = 0.02 mag.
All photometry is on the UVOT photometric system described in Poole et
al. (2008, MNRAS, 383, 627).