TITLE:   GCN CIRCULAR
NUMBER:  13490
SUBJECT: GRB 120716A: Optical decay from NOT
DATE:    12/07/19 05:52:35 GMT
FROM:    Dong Xu at Weizmann Inst  <dong.dark@gmail.com>

D. Xu (WIS), N. Groeneboom, K. Mikkelsen (U. Oslo) report on behalf of
a larger collaboration:

We observed the field of the candidate optical afterglow (Cenko et
al., GCN 13489) of GRB 120716A (Hurley et al., GCN 13487), using the
2.5m Nordic Optical Telescope (NOT) equipped with ALFOSC. Observations
started 04:03 UT on 2012-07-19 (i.e., 2.455 days after the IPN
trigger) and 5x300s SDSS r'-band images were obtained in a seeing of
~0.7".

The optical source reported in GCN 13489 is well detected in each NOT
image at coordinates

RA(J2000)=20:52:12.17
Dec(J2000)=+09:35:53.9

with an uncertainty of ~0.1 arcsec radius, being consistent with the
PTF position.

The source had r(AB)=20.10+/-0.04, calibrated with nearby SDSS stars.
The decay between the PTF and NOT epochs indicates that the source may
be the optical afterglow of GRB 120716A.