GCN Circular 25629

J. Y. Wei (NAOC), X. H. Han (NAOC), N. Dagoneau (CEA/AIM), J. Wang (GXU),
N. Leroy (CNRS/LAL)

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

We observed 16 sky regions (total: 2400 square degrees with overlaps)
to cover the skymap of the advanced LIGO/Virgo trigger S190828l,
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 9.5% prior probability
that the 16 observed and processed regions contain the true location of
the source.  The images were taken between ~5 hours and ~12 hours after
the event trigger time.

The coordinates of the 16 sky regions and observation times are listed
below:

No. Ra �Dec start-obs(UTC) �end-obs(UTC) ���Camera_TYPE

1 00:22:12.55 35:47:18.96 2019-08-28 14:58:26 2019-08-28 15:16:39 JFOV 
2 00:16:40.40 47:47:40.20 2019-08-28 14:59:15 2019-08-28 15:17:03 JFOV 
3 00:05:09.89 34:55:44.40 2019-08-28 15:00:32 2019-08-28 15:17:08 JFOV 
4 01:11:41.69 47:17:32.64 2019-08-28 15:07:01 2019-08-28 15:17:08 JFOV 
5 01:43:32.26 64:07:03.00 2019-08-28 13:53:25 2019-08-28 16:51:08 JFOV 
6 00:07:40.03 51:45:14.40 2019-08-28 16:41:24 2019-08-28 16:44:15 JFOV 
7 00:13:04.03 64:02:39.84 2019-08-28 17:05:25 2019-08-28 17:22:48 JFOV 
8 02:38:20.69 47:18:19.08 2019-08-28 17:04:13 2019-08-28 17:22:03 JFOV 
9 01:31:55.32 34:55:32.16 2019-08-28 17:09:05 2019-08-28 17:22:03 JFOV 
10 21:55:06.96 10:04:51.24 2019-08-28 16:04:03 2019-08-28 16:20:14 JFOV 
11 21:55:29.52 -1:58:15.89 2019-08-28 16:00:25 2019-08-28 16:20:14 JFOV 
12 21:59:13.44 48:02:44.52 2019-08-28 13:40:52 2019-08-28 14:06:20 JFOV 
13 22:05:10.08 34:10:09.48 2019-08-28 12:08:19 2019-08-28 19:00:58 JFOV
14 23:07:07.68 09:08:42.00 2019-08-28 17:49:12 2019-08-28 17:54:27 JFOV 
15 23:44:10.08 13:41:13.56 2019-08-28 18:09:03 2019-08-28 18:26:03 JFOV 
16 00:58:52.99 30:19:11.28 2019-08-28 17:25:15 2019-08-28 17:53:12 JFOV

The sky coverage map is available at: 
http://cmm.svom.cn/gwpub/O3/S190828l/S190828l.png
(user:svomo3 pwd:gwo3)

The weather conditions were hazy 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.