TITLE:   GCN CIRCULAR
NUMBER:  15789
SUBJECT: GRB 140206A: Nanshan optical observations
DATE:    14/02/06 13:55:07 GMT
FROM:    Dong Xu at DARK/NBI  <dong.dark@gmail.com>

D. Xu (DARK/NBI), G.-J. Feng, J. Xu, A. Esamdin, L. Ma (XAO) report:

We observed the field of GRB 140206A (Lien et al., GCN 15784; Gotz et
al., GCN 15785) using the 1m telescope located on Mt. Nanshan,
Xinjiang, China. Observations started at 12:30:16 UT on 2014-02-06
(i.e., 5.216 hr after the burst), and a series of R-band frames were
obtained.

The optical afterglow (Oksanen et al., GCN 15786; Oates & Lien, GCN
15787) is clearly detected in each of our frames, and it decayed from
M(R)=18.48+/-0.10 to m(R)=18.64+/-0.10 from 5.40 hr to 5.71 hr
post-burst, calibrated with two nearby SDSS stars. Compared with the
previous measurements in GCNs 15786 & 15788, it shows that so far the
afterglow has been decaying rather slowly and thus spectroscopy may be
doable even for a 2m class telescope in the coming hours.

Further observations are ongoing.