[vsnet-grb-info 20178] GRB 171222A: Nanshan-1m optical afterglow detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22274
SUBJECT: GRB 171222A: Nanshan-1m optical afterglow detection
DATE:    17/12/23 14:00:59 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu at nao.cas.cn>

X. Zhang, P. Zong, J.H. Liu (XAO), H.X. Feng, Z.P. Zhu, D. Xu (NAOC), 
H.B. Niu, J.Z. Liu, A. Esamdin, L. Ma, Y. Zhang (XAO) report on behalf 
of a larger collaboration:

We observed the field of GRB 171222A (Racusin et al., GCN 22265) using 
the 1m telescope located at Nanshan, Xinjiang, China. We obtained 6x300s 
R-band frames, starting at 18:14:36 UT on 2017-12-22, i.e., 1.83 hr 
after the BAT trigger.

An uncatalogued and fading optical transient (OT) is detected at the XRT 
position (Osborne et al., GCN 22266) as well as the NOT position (Perley 
et al., GCN 22269) in our images. Preliminary photometry results are as 
follows:

Tmid-T0 Exposure  Filter    Mag(R)    MagErr(R)
(hr)           (s)
1.87        1x300       R        20.86        0.21
2.68        3x300       R        21.47        0.22
7.87        2x300       R        21.72        0.22

Photometry is calibrated with nearby USNO-B1.0 stars (R2 magnitudes), 
and errors are only statistical values. We thus conclude that this OT is 
the optical afterglow of GRB 171222A.