TITLE:   GCN CIRCULAR
NUMBER:  10193
SUBJECT: GRB 091127: Swift/UVOT Detection of an Optical Afterglow
DATE:    09/11/28 00:55:41 GMT
FROM:    Stefan Immler at NASA/GSFC  <stefan.m.immler@nasa.gov>

GRB 091127: Swift/UVOT Detection of an Optical Afterglow

S. Immler (CRESST/UMCP/GSFC) and E. Troja (NASA/GSFC/ORAU) report
on behalf of the Swift UVOT Team:

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 3219 seconds after the BAT trigger. There is an afterglow in
the rapidly available 2.7'x2.7' sub-image at
   RA(J2000)  =    02:26:19.89 = 36.58288
   DEC(J2000) = -18:57:08.5  = -18.95235
with a 90%-confidence error radius of about 0.61 arc sec. This position
is 40.9 arc sec. from the center of the BAT error circle. The estimated
magnitude is 16.21 with a 1-sigma error of about 0.14. No correction has
been made for the expected extinction corresponding to E(B-V) of 0.04.

The optical afterglow position is consistent with the Liverpool Telescope
afterglow candidate (Smith et. al GCN 10192) that was detected with a
magnitude of around R=15.0.