TITLE:   GCN CIRCULAR
NUMBER:  17869
SUBJECT: GRB 150523A: LCOGT FTS afterglow confirmation
DATE:    15/05/25 10:06:33 GMT
FROM:    Simone Dichiara at Ferrara U/Italy  <dichiara@fe.infn.it>

S. Dichiara, C. Guidorzi (U. Ferrara), S.Kobayashi (LJMU),
C.G. Mundell (U. Bath), A. Gomboc (U. Ljubljana) on behalf
of a larger collaboration report:

On May 24 we re-observed GRB 150523A (Yu et al GCN 17863;
Bissaldi et al. GCN 17864) using the 2-m Faulkes Telescope South
(FTS) with SDSS r and i filters, starting from 08:53 UT (~23.4 hours
post burst). Compared with our previous report (Dichiara et al.
GCN 17868) the optical candidate appears to have significantly
faded, as follows:

Mid time(hrs)    Exp(s)       Filter   Magnitude
-----------------------------------------------
13.87            10x120          r'    20.45 +- 0.15
23.69            10x120          r'    21.20 +- 0.22
-----------------------------------------------

The corresponding average power-law decay index is 1.3 +- 0.5.
Magnitudes are calibrated against USNOB-1 nearby stars.
We therefore confirm the afterglow nature of the optical
candidate previously reported.