[vsnet-grb-info 12280] GRB 120817A: FTN and FTS observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13664
SUBJECT: GRB 120817A: FTN and FTS observations
DATE:    12/08/17 11:02:47 GMT
FROM:    Cristiano Guidorzi at Ferrara U,Italy  <guidorzi at fe.infn.it>

C. Guidorzi (U. Ferrara), C.G. Mundell, C.J. Mottram,
F. Virgili (LJMU), A. Gomboc (U. Ljubljana) report on
behalf of a larger collaboration:

The 2-m Faulkes Telescope North (FTN) automatically began observing
GRB 120817A (Gompertz et al. GCN Circ. 13661) on August 17 2012,
06:53:57 UT corresponding to 4.2 minutes post burst trigger
with BVRi' filters. Within the XRT error circle (Perri et al.
GCN Circ. 13662), close to a USNOB1 object we detect a faint,
uncatalogued, possibly fading source at the following position

R.A. = 16:42:45.92
Dec = -38:21:12.4   (J2000)

with an uncertainty of about 1".
The detection is marginal, with an estimated magnitude of
19.3 +/- 0.4 in the R band at a mean time of 17.4 minutes
(60 s exposure) calibrated against nearby USNOB-1 stars.

The 2-m Faulkes Telescope South (FTS) began observing at 77 min
post burst. In a stacked R-band frame we find marginal evidence
for fading, with R=19.8 +- 0.3 mag at a mean time of 105 min
(total exposure of 360 s). The nearby USNOB1 object is compatible
with being constant between the two observations.

The comparison between the FTN and FTS R-band images is available at
http://www.fe.infn.it/u/guidorzi/GRB120817A_XRT_FT_candidate.jpg