[vsnet-grb-info 15794] GRB 141121A: LCO-FTN observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17082
SUBJECT: GRB 141121A: LCO-FTN observations
DATE:    14/11/21 12:46:18 GMT
FROM:    Cristiano Guidorzi at Ferrara U,Italy  <guidorzi at fe.infn.it>

S. Dichiara and C. Guidorzi (U. Ferrara) on behalf of
a large collaboration report:

The Las Cumbres Observatory 2-m Faulkes Telescope North in
Hawaii began observing Swift GRB 141121A (Lien et al. GCN
Circ 17075) on November 21 at 10:42:54 UT, i.e. ~6.9 hours
after the BAT trigger, with the r' and i' filters.

We clearly detect the optical afterglow (Tanga et al.
GCN 17078; Perley et al. GCN 17081) with the following
magnitudes:

Mid time from  Total Exp   Filter    Magnitude
trigger (hr)   (s)
-------------------------------------------------
7.0            120x5       r'        19.62 +- 0.06
7.2            120x5       i'        19.42 +- 0.06
-------------------------------------------------

Magnitudes are calibrated against nearby SDSS stars.
Compared with GROND values we note a possible hint
for rebrightening or, in any case, for a very shallow
decay between the two epochs.