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
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.