GCN Circular 20745

J.Y. Wei (NAOC), X.H. Han (NAOC), X.M. Meng (NAOC), N. Leroy (LAL),
 S. Antier (LAL), C. WU (NAOC), L.P. Xin (NAOC), L. Huang (NAOC),
Y. Xu (NAOC), H.B. Cai (NAOC), J. Wang (NAOC), X.M. Lu (NAOC),
Y.L. Qiu (NAOC), J.S. Deng (NAOC), L. Cao (NAOC), S. Wang (NAOC),
L. Jia (NAOC), S.C. Zou (NAOC), S.F. Liu (NAOC), Q.C. Feng (NAOC),
H.L. Li (NAOC), D.W. Xu (NAOC), Y.J. Xiao (NAOC), W.L. Dong (NAOC),
Y.T. Zheng (NAOC), E.W.Liang (GXU), X.G.Wang (GXU), Y.G. Yang (HBNU),
B. Cordier (CEA), S.N. Zhang (NAOC), D. Dornic (CPPM), B.B. Wu (IHEP),
J.L. Atteia (IRAP), D. G?tz (CEA), C.Lachaud (APC),
on behalf of the SVOM Gravitational Astronomy group report:

We observed about 3200 square degree (8 sky regions) of the skymap
of the advanced LIGO trigger G275404, with SVOM/Mini-GWAC, at Xinglong
Observatory of NAOC equipped with U9000 camera (FOV~400 square
degree/camera).
SVOM/Mini-GWAC comprises 12 wide field angle cameras (aperture=7cm),
working with unfiltered band. The observations are operated in time-series
mode, taking one exposure in 15 seconds (10s exposure + 5s readout).
The limit magnitude is ~12 mag in R band. We estimate a 46.6% prior
probability that these 8 regions contain the true location of the
source.

The coordinates of the 8 regions and observation time are list following:

start-obs(UTC)  end-obs(UTC)    Ra      Dec     Camera_ID
2017-02-25      19:23:51.9      2017-02-25      20:41:04.7      10:33:59.6
     +30:12:22                       C3
2017-02-25      19:23:51.9      2017-02-25      20:41:06.2      10:38:05.6
     +10:07:57                       C4
2017-02-25      19:23:42.2      2017-02-25      22:13:19.6      17:18:04.0
     +69:28:00                       C5
2017-02-25      19:23:44.7      2017-02-25      22:13:38.0      17:21:47.1
     +50:28:32                       C6
2017-02-25      13:01:04.2      2017-02-25      21:37:38.1      09:21:25.5
     +69:40:01                       C7
2017-02-25      13:01:04.2      2017-02-25      21:37:39.7      09:23:01.6
     +50:00:25                       C8
2017-02-25      21:39:38.3      2017-02-25      22:13:28.5      20:00:36.6
     +69:38:42                       C7
2017-02-25      21:39:38.3      2017-02-25      22:13:25.5      20:01:12.7
     +50:00:21                       C8

The first image (which is covered in our routine survey) was taken
 ~5 hours 29 minutes before the event trigger. No any significant
transient is found in our online pipeline. The image analysis is
ongoing in detailed processing with our offline pipeline.