TITLE:   GCN CIRCULAR
NUMBER:  6641
SUBJECT: GRB070721B: A bright UVOT candidate
DATE:    07/07/21 12:05:59 GMT
FROM:    Patricia Schady at MSSL/Swift  <ps@mssl.ucl.ac.uk>

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

The Swift/UVOT observed the field of GRB 070721B and took a finding chart 
exposure of 100 seconds with the White (160-650 nm) filter starting ~50 
seconds after the BAT trigger. A candidate afterglow was found on-board in 
the rapidly available 2.7'x2.7' sub-image, consistent with the XRT 
position (Ziaeepour et al., GCN 6640) at
   RA(J2000)  =  02:12:32.95 =  33.1373 degrees
   DEC(J2000) = -02:11:40.6  =  -2.1946 degrees
with a 1-sigma error radius of about 0.9 arc sec. This position is 9.7 
arcsec. from the center of the BAT error circle. The estimated magnitude 
is 15.9 with a 1-sigma error of about 0.5 mag. No correction has been made 
for the estimated Galactic reddenning of E(B-V)=0.02 mag (Schlegel, 
Finkbeiner & Davic, 1998)