[vsnet-grb-info 17220] GRB 151111A: LCOGT-FTS afterglow observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18581
SUBJECT: GRB 151111A: LCOGT-FTS afterglow observations
DATE:    15/11/11 17:05:15 GMT
FROM:    Simone Dichiara at Ferrara U/Italy  <dichiara at fe.infn.it>

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

The 2-m LCOGT Faulkes Telescope South began observing Swift
GRB 151111A (McCauley et al. GCN 18578) on November 11, 10:45 UT
(2.2 hours after the burst trigger) with SDSS R and I filters
under poor sky conditions. We do not detect any optical afterglow
candidate within the enhanced Swift-XRT error circle
(Goad et al. GCN 18579) with the following magnitudes:

Mid Time      Exposure       Filter       Magnitude
(hours)           (s)
-------------------------------------------------------
3.5            10x120         R           > 20.5
4.2             9x120         I           > 20.0
-------------------------------------------------------

Calibration is done against nearby USNOB-1 stars using R2 and I
nominal magnitudes.
We note in both filters the presence of a possible source of
R~21 mag at the following position: RA(J2000)=03:47:22.75,
DEC(J2000)=-44:09:43.6 (error radius of 1.5"). We caution that
the detection is not significant, so we cannot rule out the
possibility that it is a fluke.