GCN Circular 27221

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.