TITLE:   GCN CIRCULAR
NUMBER:  6959
SUBJECT: GRB 071021: Faulkes Telescope South optical candidate
DATE:    07/10/21 10:47:13 GMT
FROM:    Andrea Melandri at Liverpool John Moores U  <axm@astro.livjm.ac.uk>

C. Guidorzi (U. Bicocca & INAF-OAB), A. Melandri, I.A. Steele,
R.J. Smith, C.J. Mottram, M.F. Bode, D. Carter, S. Kobayashi,
D.F. Bersier, C.G. Mundell (Liverpool JMU), A. Gomboc (U. Ljubljana),
P. O'Brien, E. Rol, N. Bannister (U. Leicester) report:


The 2-m Faulkes Telescope South robotically followed up GRB071021
(Sakamoto et al., GCN Circ. 6958) beginning 258 seconds after the GRB
trigger time (UT 09:41:33).

We detect a fading uncatalogued source at

RA  =  22:42:35.41
Dec = +23:43:08.9

with un uncertainty of 0.7 arcsec on both coordinates. This position
is 11.4 arcsec from the centre of first XRT error circle (Sakamoto et
al., GCN Circ. 6958).

We measure a magnitude of R = 17.8 +/- 0.3 for a 3x10 seconds coadded
frame, from 258 to 308 seconds after the trigger time. In subsequent
images the source clearly faded.

Magnitudes are calibrated with respect to R2 mag of several nearby
USNO-B1 objects. Observations are still ongoing.