[vsnet-grb-info 25068] LIGO/Virgo S200219ac: no counterpart candidate in SVOM/GWAC observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27169
SUBJECT: LIGO/Virgo S200219ac: no counterpart candidate in SVOM/GWAC observations
DATE:    20/02/23 16:49:40 GMT
FROM:    Jean-Gregoire Ducoin at LAL  <ducoin at lal.in2p3.fr>

J.-G. Ducoin(IJCLab), X. G. Wang (GXU), N. Leroy (CNRS/LAL), 
J. R. Mao (YNAO), S. S. Sun (GXU)

report on behalf of the SVOM Multi Messenger Astronomy and GWAC teams
(http://www.svom.fr/en/svom-mma-and-gwac-team):

We observed 13 (~1950 square deg) sky regions to cover the skymap of the
advanced LIGO/Virgo trigger S200219ac  (GCN # 27130), 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 42.7% of the probability of the advanced LIGO/Virgo skymap.
Images were taken between ~3 hours and ~8 hours
after the GW trigger time. The coordinates of the 13 sky regions
observed and their observation times and covered probability are
listed below:


Id Ra          Dec      start (UTC)         end (UTC)          Proba. Cam.
1  10:18:57.60 31:33:11 2020-02-19 12:30:12 2020-02-19 12:58:20 0.002 JFOV
2  11:10:06.00 19:17:33 2020-02-19 12:30:12 2020-02-19 12:58:20 0.024 JFOV
3  10:21:27.60 19:30:50 2020-02-19 12:30:12 2020-02-19 12:58:20 0.009 JFOV
4  11:00:30.00 18:22:24 2020-02-19 12:01:13 2020-02-19 12:29:28 0.024 JFOV
5  11:15:24.24 35:32:37 2020-02-19 12:30:20 2020-02-19 13:30:58 0.114 JFOV
6  11:34:14.64 31:33:03 2020-02-19 13:32:46 2020-02-19 14:00:55 0.106 JFOV
7  11:36:40.32 19:31:06 2020-02-19 13:32:46 2020-02-19 14:00:55 0.008 JFOV
8  11:51:46.80 48:34:54 2020-02-19 14:03:35 2020-02-19 15:03:39 0.096 JFOV
9  11:57:32.16 36:34:18 2020-02-19 14:03:35 2020-02-19 15:03:39 0.090 JFOV
10 12:54:39.12 52:06:30 2020-02-19 13:41:16 2020-02-19 14:42:13 0.115 JFOV
11 13:34:29.04 65:10:48 2020-02-19 15:45:36 2020-02-19 17:19:54 0.058 JFOV
12 13:49:30.96 53:16:58 2020-02-19 15:44:30 2020-02-19 17:19:54 0.007 JFOV
13 15:15:08.40 68:44:16 2020-02-19 15:49:58 2020-02-19 16:46:14 0.010 JFOV



The sky coverage map is available at:
http://cmm.svom.cn/gwpub/O3/S200219ac/S200219ac.png
(user:svomo3 pwd:gwo3).

Weather conditions were clear 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.