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GCN Circular 27221

LIGO/Virgo S200225q: no counterpart candidate in SVOM/GWAC observations
2020-02-26T09:41:33Z (4 years ago)
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

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:
(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
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