TITLE:   GCN CIRCULAR
NUMBER:  15531
SUBJECT: GRB 131127B: Nanshan optical observations
DATE:    13/11/28 13:25:05 GMT
FROM:    Dong Xu at DARK/NBI  <dong.dark@gmail.com>

D. Xu (DARK/NBI), H.-B. Niu, J.-Z. Liu, G.-J. Feng, C.-H. Bai, A.
Esamdin, L. Ma (XAO) report:

We observed the fields of the three afterglow candidates of GRB
131127B (von Kienlin, GCN 15528; Singer & Kasliwal, GCN 15524;
Golenetskii et al., GCN 15530), using the 1m telescope located on Mt.
Nanshan, Xinjiang, China. Observations started at 11:37:34 UT on
2013-11-28, (i.e., 21.42 hr after the Fermi trigger) and a series of
R-band frames were obtained.

The three optical afterglow candidates are clearly detected in their
stacked images.

For the one dubbed iPTF13ecv, we measure its magnitude
m(R)=18.66+/-0.14, calibrated with two nearby SDSS stars and using the
Lupton (2005) transformation. This magnitude is basically consistent
with the value reported in Singer & Kasliwal (GCN 15524), indicating
that its significant fading is ruled out.

For the other two dubbed iPTF13ect and iPTF13ecu, given that they are
very close to the cores of the galaxies and not well resolved in our
images, we are not able to put good constraints on their magnitudes at
the moment.