[vsnet-grb-info 8430] GRB 090927: Swift/UVOT detection of an optical afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9946
SUBJECT: GRB 090927: Swift/UVOT detection of an optical afterglow
DATE:    09/09/27 10:58:19 GMT
FROM:    Caryl Gronwall at PSU/Swift-UVOT  <caryl at astro.psu.edu>

C. Gronwall and D. Grupe (PSU) report on behalf of the Swift/UVOT team:

In response to GRB090927 (Swift/BAT trigger 370846) at 10:07:16 UT,
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 2141 seconds after the BAT trigger. There is a candidate  
afterglow in
the rapidly available 2.7'x2.7' sub-image at
RA(J2000) =	22:55:53.41 = 343.97255
DEC(J2000) = -70:58:49.3 = -70.98037
with a 90%-confidence error radius of about 0.63 arc sec. This  
position is 7.2
arc sec. from the center of the XRT error circle. The estimated  
magnitude is
19.10 with a 1-sigma error of about 0.15. No correction has been made  
for the
expected extinction corresponding to E(B-V) of 0.03.