[vsnet-grb-info 23549] LIGO/Virgo S190901ap: no counterpart candidate in the SVOM/GWAC observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25648
SUBJECT: LIGO/Virgo S190901ap: no counterpart candidate in the SVOM/GWAC observations
DATE:    19/09/04 08:21:17 GMT
FROM:    Xuhui Han at NAOC/SVOM  <hxh at nao.cas.cn>

J. Y. Wei (NAOC), X. H. Han (NAOC), S. Antier (CNRS/APC), J. Wang (GXU),
N. Leroy (CNRS/LCL), L. P. Xin (NAOC)

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

We observed 23 sky regions (total: 3450 square degrees with overlaps)
to cover the skymap of the advanced LIGO/Virgo trigger S190901ap,
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 21.1% prior 
probability that the 23 observed and processed regions contain 
the true location of the source. The images were taken between ~12
hours and ~21 hours after the event trigger time.

The coordinates of the 23 sky regions and observation times are listed
below:

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

1 14:52:45.36 36:27:42.12  2019-09-02 11:50:35 2019-09-02 12:57:50 JFOV
2 14:47:05.52 48:27:28.80  2019-09-02 12:52:10 2019-09-02 12:57:50 JFOV
3 16:04:10.80 30:49:03.00  2019-09-02 11:41:44 2019-09-02 11:47:24 JFOV
4 15:09:00.24 18:30:39.60  2019-09-02 11:50:38 2019-09-02 11:54:17 JFOV
5 15:07:09.12 30:35:42.36  2019-09-02 11:50:39 2019-09-02 11:54:17 JFOV
6 15:26:18.24 15:16:59.88  2019-09-02 13:08:45 2019-09-02 13:26:57 JFOV
7 16:02:03.12 35:25:58.44  2019-09-02 13:05:29 2019-09-02 13:21:17 JFOV
8 16:39:42.96 27:17:34.80  2019-09-02 12:08:56 2019-09-02 12:23:06 JFOV
9  01:16:21.62 -15:31:53.40 2019-09-02 16:24:34 2019-09-02 16:52:31 JFOV
10 17:19:00.24 52:14:09.60  2019-09-02 14:45:41 2019-09-02 14:56:13 JFOV
11 18:05:18.24 01:30:15.52  2019-09-02 13:51:32 2019-09-02 13:52:21 JFOV
12  02:28:14.83 -15:30:36.00 2019-09-02 17:27:23 2019-09-02 19:01:31 JFOV
13  03:19:23.62 -3:14:21.77  2019-09-02 17:31:26 2019-09-02 17:52:54 JFOV
14  03:58:00.72 -1:57:11.38  2019-09-02 17:34:35 2019-09-02 17:49:09 JFOV
15  03:41:15.24 01:27:46.30  2019-09-02 18:01:48 2019-09-02 18:22:04 JFOV
16  04:31:50.62 13:46:42.60  2019-09-02 18:01:48 2019-09-02 18:14:22 JFOV
17  04:08:53.54 15:03:23.04  2019-09-02 16:59:48 2019-09-02 20:27:27 JFOV
18  04:44:53.30 35:53:54.24  2019-09-02 18:04:30 2019-09-02 18:21:05 JFOV
19  04:53:17.66 01:30:11.16  2019-09-02 19:14:43 2019-09-02 20:04:18 JFOV
20  05:43:52.15 13:49:17.40  2019-09-02 19:22:00 2019-09-02 19:53:46 JFOV
21  04:52:20.66 -15:27:02.16 2019-09-02 20:16:15 2019-09-02 20:35:42 JFOV
22  05:43:23.81 -3:10:38.86  2019-09-02 20:26:22 2019-09-02 20:35:42 JFOV
23  05:24:02.42 14:49:40.80  2019-09-02 18:40:24 2019-09-02 18:52:32 JFOV

The sky coverage map is available at: 
http://cmm.svom.cn/gwpub/O3/S190901ap/S190901ap.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.