GCN Circular 25970

C.Lachaud (APC), X. G. Wang (GXU), A. Coleiro (APC),
J.R. Mao (YNAO), G. W. Li (NAOC)

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

We observed 27 sky regions (total: 4050 square degrees with overlaps)
to cover the skymap of the advanced LIGO/Virgo trigger S190930s,
with SVOM/GWAC, at Xinglong Observatory equipped with a set of two
types of wide angle cameras: FFOV cameras (FOV~900 square degrees/camera,
aperture = 3.5 cm) and JFOV cameras (FOV~150 square degrees/camera,
aperture = 18 cm). SVOM/GWAC currently comprises 4 FFOV cameras and
16 JFOV cameras, working with unfiltered band. The observations are
operated in time-series mode, taking one exposure every 25 seconds
(20s exposure + 5s readout). We estimate a 77.2% prior
probability that the observed and processed regions contain
the true location of the source. The images were taken between
~15 minutes before and ~5 hours after the event trigger time.

The coordinates of the 27 sky regions observed after the trigger
and their observation times are listed below:

No. Ra  Dec start-obs(UTC)  end-obs(UTC)    Camera_TYPE
1  01:45:10.30 57:37:14.52 2019-09-30 17:15:39 2019-09-30 17:28:37 JFOV
2  02:13:24.41 68:57:30.24 2019-09-30 17:17:17 2019-09-30 17:23:45 JFOV
3  21:18:19.68 68:54:10.44 2019-09-30 15:10:18 2019-09-30 15:31:18 JFOV
4  20:49:49.20 57:34:23.88 2019-09-30 15:14:18 2019-09-30 15:31:18 JFOV
5  20:08:15.60 30:22:52.32 2019-09-30 14:28:46 2019-09-30 14:58:59 JFOV
6  21:05:10.80 30:36:19.08 2019-09-30 14:38:29 2019-09-30 14:55:29 JFOV
7  21:12:28.32 23:45:53.64 2019-09-30 15:56:29 2019-09-30 16:23:11 JFOV
8  20:23:50.64 24:02:03.12 2019-09-30 16:09:50 2019-09-30 16:24:24 JFOV
9  21:18:24.48 35:26:04.92 2019-09-30 16:24:23 2019-09-30 16:24:23 JFOV
10 21:45:58.80 52:18:05.04 2019-09-30 16:28:13 2019-09-30 16:45:12 JFOV
11 21:34:48.24 40:42:21.24 2019-09-30 16:28:37 2019-09-30 16:56:08 JFOV
12 20:35:59.04 40:59:54.60 2019-09-30 16:48:26 2019-09-30 16:56:08 JFOV
13 21:19:55.20 01:30:02.95 2019-09-30 13:54:35 2019-09-30 16:26:11 JFOV
14 20:29:44.16 13:30:14.04 2019-09-30 13:54:35 2019-09-30 16:24:15 JFOV
15 21:20:11.76 13:41:14.64 2019-09-30 13:54:35 2019-09-30 16:20:36 JFOV
16 02:35:50.35 35:29:03.84 2019-09-30 17:40:06 2019-09-30 18:01:35 JFOV
17 21:20:36.48 57:56:40.56 2019-09-30 13:54:12 2019-09-30 14:24:03 JFOV
18 23:12:45.60 68:55:31.80 2019-09-30 13:54:12 2019-09-30 14:24:03 JFOV
19 22:45:54.48 64:26:27.96 2019-09-30 16:30:13 2019-09-30 16:43:11 JFOV
20 20:52:14.16 64:01:55.92 2019-09-30 16:32:14 2019-09-30 16:32:14 JFOV
21 22:27:42.00 23:44:02.04 2019-09-30 18:01:32 2019-09-30 18:24:10 JFOV
22 21:39:04.08 24:00:06.12 2019-09-30 13:26:16 2019-09-30 18:24:10 JFOV
23 22:33:36.00 35:24:57.24 2019-09-30 13:40:48 2019-09-30 18:24:10 JFOV
24 22:42:58.56 13:51:07.56 2019-09-30 17:40:48 2019-09-30 18:00:13 JFOV
25 21:44:38.40 47:20:02.04 2019-09-30 18:07:20 2019-09-30 18:35:18 JFOV
26 22:52:12.24 35:28:24.60 2019-09-30 18:07:21 2019-09-30 18:35:18 JFOV
27 03:40:37.78 64:29:39.84 2019-09-30 17:29:25 2019-09-30 17:29:25 JFOV

The sky region #22 was observed at the time of the trigger (it has
3.5% probability to contain the true location of the source).

Some sky regions have been observed before the GW event
for a total of 1200 square degrees with overlap
(from ~2 hours to ~ 12 minutes before the event) :

No. Ra  Dec start-obs(UTC)  end-obs(UTC)    Camera_TYPE
1 21:23:18.96 35:17:43.08 2019-09-30 12:53:59 2019-09-30 13:22:59 JFOV
2 20:17:48.24 47:21:36.72 2019-09-30 12:52:55 2019-09-30 13:22:59 JFOV
3 22:32:05.04 13:41:29.40 2019-09-30 11:42:57 2019-09-30 12:14:29 JFOV
4 22:31:43.92 01:29:58.74 2019-09-30 11:43:44 2019-09-30 12:11:29 JFOV
5 21:41:35.52 13:30:04.68 2019-09-30 11:43:44 2019-09-30 12:12:59 JFOV
6 23:13:06.96 52:21:46.08 2019-09-30 11:43:42 2019-09-30 12:08:27 JFOV
7 22:02:56.88 41:04:53.76 2019-09-30 12:06:12 2019-09-30 12:12:27 JFOV
8 23:01:46.32 40:46:03.72 2019-09-30 12:08:57 2019-09-30 12:12:27 JFOV

The sky coverage map is available at:
http://cmm.svom.cn/gwpub/O3/S190930s/S190930s_post.png
(user:svomo3 pwd:gwo3)

The weather condition was clear during the observations. A 3 sigma
limiting magnitude of about 16.3 mag in R band was obtained in the single
frames. No credible new source is 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.