[vsnet-grb-info 17171] GRB 151027B: LCOGT FTN afterglow observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18520
SUBJECT: GRB 151027B: LCOGT FTN afterglow observations
DATE:    15/10/28 20:13:07 GMT
FROM:    Simone Dichiara at Ferrara U/Italy  <dichiara at fe.infn.it>

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

The 2-m Faulkes Telescope North in Hawaii began observing Swift
GRB 151027B (Ukwatta et al., GCN 18499) on October 28, 12:18:25 UT, i.e.,
~ 13.6 hours after the burst trigger, with the r' and i' filters.

Although we did not detect the optical counterpart (Malesani et al.,
 GCN 18501; Xu et al., GCN 18505; Wiseman et al., GCN 18507;
Buckley et al., GCN 18511; Watson et al., GCN 18512) in the r'
filter (R > 20.3), the source is detected in the i' filter with
I = 19.6 +/- 0.3 mag at a mid time of 13.9 hours post burst
(total exposure in i' of 600 s).

The magnitude is calibrated against nearby USNO-B1 stars.