GCN Circular 8509
S. Immler (CRESST/UMD/GSFC), N. P. M. Kuin (MSSL/UCL), and S. T. Holland (CRESST/USRA/GSFC) report on behalf of the Swift UVOT team: Further analysis of Swift Ultraviolet/Optical Telescope (UVOT) data of GRB 081109A (Immler et al., GCN Circ. 8500), starting 75 sec after the BAT trigger, gives a tentative detection of an optical source at the reported REM position (D'Avanzo et al., GCN Circ 8501) in the white filter at a 3.3-sigma level of confidence. The source is not detected in any of the other UVOT filters at the limiting magnitudes reported below. Filter Tstart(s) Tstop(s) Exp(s) Magnitude wh 75 6592 745 21.6+/-0.3 u 287 6181 501 >21.5 (3-sigma UL) b 543 6387 452 >20.9 (3-sigma UL) uvw2 593 5362 274 >21.6 (3-sigma UL) v 617 5566 274 >20.9 (3-sigma UL) uvm2 641 5771 274 >21.5 (3-sigma UL) uvw1 666 5976 255 >21.5 (3-sigma UL) The possible detection in the white filter, combined with the lack of a detection in the v filter, is consistent with the source having a redshift greater than 5.5. Follow-up observations, especially in the infrared, are encouraged.