TITLE:   GCN CIRCULAR
NUMBER:  16789
SUBJECT: GRB 140907A : Optical observations from Nanshan
DATE:    14/09/07 18:03:54 GMT
FROM:    Dong Xu at DARK/NBI  <dong.dark@gmail.com>

D. Xu (DARK/NBI), X. Gao (Urumqi No.1 Senior High School, Xinjiang),
G.-J. Feng, A. Esamdin, L. Ma (XAO), Z.-J. Xu (Nanjing Putian
Telecommunications Co. Ltd., Jiangsu) report:

We observed the field of GRB 140907A (Krimm et al., GCN 16788) using
the 35cm robotic telescope and the 1m optical telescope located at
Nanshan, Xinjiang, China. The observations started at 16:18:42 UT on
2014-09-07 at the 35cm telescope without any filter, and 16:34:28 UT
at the 1m telescope in the R filter.

The afterglow is well detected in our images at coordinates

R.A. (J2000) = 03:12:34.98
Dec. (J2000) = +46:36:17.2

Error radius: ~ 0.7 arcsec

which is fully consistent with the UVOT position. Generally, the
afterglow has been decaying, and follows are the preliminary
measurements from the 35cm telescope:

     Mid-Time              Mag
2014/09/07.68001     16.7
2014/09/07.68083     16.7
2014/09/07.68164     16.7
2014/09/07.68244     16.9
2014/09/07.68325     17.0
2014/09/07.68405     17.1
2014/09/07.68485     17.0
2014/09/07.68565     16.9
2014/09/07.68646     17.2

with a typical error of 0.2 magnitude, calibrated with the R-band
catalog of NET CMC-14.

Observations are ongoing.