TITLE: GCN CIRCULAR NUMBER: 27221 SUBJECT: LIGO/Virgo S200225q: no counterpart candidate in SVOM/GWAC observations DATE: 20/02/26 09:41:33 GMT FROM: Jirong Mao at Yunnan Obs J. Mao (YNAO), N. Leroy (IJCLab), X. G. Wang (GXU), D. Corre (IJCLab), J. Y. Wei (NAOC) report on behalf of the SVOM Multi Messenger Astronomy and GWAC teams (http://www.svom.fr/en/svom-mma-and-gwac-team): We observed 6 (~900 square deg) sky regions to cover the skymap of the advanced LIGO/Virgo trigger S200225q (GCN # 27193), with SVOM/GWAC, at Xinglong Observatory. SVOM/GWAC is equipped with two sets of wide angle cameras: - FFOV cameras (FOV~900 square degrees/camera, aperture = 3.5 cm), - JFOV cameras (FOV~150 square degrees/camera, aperture = 18 cm). SVOM/GWAC currently comprises 4 FFOV cameras and 16 JFOV cameras, working in the unfiltered band. The observations are operated in time-series mode, taking one exposure every 25 seconds (20s exposure + 5s readout). The observed and processed regions enclosed an estimated 56.5% of the probability of the advanced LIGO/Virgo skymap. Images were taken between ~5.5 hours and ~6.5 hours after the GW trigger time. The coordinates of the 6 sky regions observed and their observation times and covered probability are listed below: Id Ra Dec start (UTC) end (UTC) Proba. Cam. 1 05:56:47.7 65:08:15 2020-02-25 11:42:19 2020-02-25 12:33:05 0.001 JFOV 2 07:26:34.3 52:57:54 2020-02-25 11:34:41 2020-02-25 12:02:57 0.197 JFOV 3 06:34:13.4 31:32:25 2020-02-25 11:03:34 2020-02-25 11:31:49 0.142 JFOV 4 06:19:52.5 30:20:19 2020-02-25 11:03:45 2020-02-25 11:31:57 0.085 JFOV 5 07:28:23.2 63:59:54 2020-02-25 12:36:01 2020-02-25 12:36:25 0.165 JFOV 6 07:04:46.5 36:07:24 2020-02-25 11:48:36 2020-02-25 12:32:32 0.170 JFOV The sky coverage map is available at: http://cmm.svom.cn/gwpub/O3/S200225q/S200225q.png (user:svomo3 pwd:gwo3). Weather conditions were hazy during the observations. An average 3-sigma limiting magnitude of 16 mag in the R band was obtained in the single frames. No credible new source was detected by our online pipeline during follow-up observations. A more detailed image analysis including co-addition is ongoing with our offline pipeline to search for transient candidates.