LIGO/Virgo G275404: SVOM/Mini-GWAC: Observations of initial skymap

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.