[vsnet-grb-info 22561] LIGO/Virgo S190521r: No optical counterpart from SVOM/GWAC-F30 observations.

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  24660
SUBJECT: LIGO/Virgo S190521r: No optical counterpart from SVOM/GWAC-F30 observations.
DATE:    19/05/24 11:46:57 GMT
FROM:    Damien Turpin at NAOC (CAS)  <dturpin-astro at hotmail.com>

LIGO/Virgo S190521r: No optical counterpart from SVOM/GWAC-F30 observations.

D. Turpin (NAOC), N. Dagoneau (CEA/AIM), L.P. Xin (NAOC),
X.H. Han (NAOC), J.Y. Wei (NAOC), C. Wu (NAOC),  L. Huang (NAOC),
Y. Xu (NAOC), H.B. Cai (NAOC), J. Wang (NAOC), X.M. Lu (NAOC),
Y.L. Qiu (NAOC), J.S. Deng (NAOC), L. Jia (NAOC), S.C. Zou (NAOC), 
S.F. Liu (NAOC), Q.C. Feng (NAOC), H.L. Li (NAOC), D.W. Xu (NAOC),
Y.J. Xiao (NAOC), W.L. Dong (NAOC), Y.T. Zheng (NAOC), P.P. Zhang (NAOC),
R.S. Zhang (NAOC), E.W. Liang (GXU), X.G. Wang (GXU), Z.G. Dai (NJU),
X.Y. Wang (NJU), Y.G. Yang (HBNU), J.R. Mao (YNAO), B. Cordier (CEA/AIM),
S. Basa (CNRS/LAM), J.L. Atteia (UPS/IRAP), D. Götz (CEA/AIM),
A. Claret (CEA/AIM), N. Leroy (CNRS/LAL), C. Lachaud (CNRS/APC), 
E. Le Floc'h (CEA/AIM), S.N. Zhang (IHEP), B.B. Wu (IHEP),
report on behalf of the SVOM Ground Follow-up Group:


We observed 12 sky regions to cover the initial skymap of the 
LIGO/Virgo trigger S190521r (GCN24632), with the SVOM/GWAC-F30 
telescope operated by Huaibei Normal University and NAOC, CAS 
at Xinglong Observatory, China. 
The SVOM/GWAC-F30 is equipped with Standard Johnson filters
and 3Kx3K FLI CCD (FOV~1.8x1.8 degree). The GWAC-F30 is using
tiling observation strategy. The tiles are calculated to cover
the most probable regions of the 90% localization area given in the
GW probability skymap. Several images with a single exposure of 60s
time in R band are taken for each tile.

The 12 tile coordinates and the observation periods are listed below:

# Ra[hms] Dec[dms] start-obs[UTC] Total_exp[s] N_image R_lim
1 18:21:52.801 +14:27:00.00 2019-05-21T14:25:25.305 300.0 5 14.26
2 18:32:50.399 +17:51:00.00 2019-05-21T14:32:37.560 300.0 5 14.11
3 18:30:21.600 +16:08:60.00 2019-05-21T14:35:33.417 300.0 5 16.38
4 19:08:35.999 +22:57:00.00 2019-05-21T14:45:16.739 300.0 5 13.38
5 19:15:40.799 +24:39:00.00 2019-05-21T14:55:28.205 300.0 5 14.23
6 18:02:52.800 +09:21:00.00 2019-05-21T15:04:44.953 300.0 5 14.72
7 18:37:23.999 +16:08:60.00 2019-05-21T15:13:00.797 300.0 5 15.53
8 18:08:12.001 +11:03:00.00 2019-05-21T15:21:21.874 300.0 5 14.03
9 18:07:33.600 +12:45:00.00 2019-05-21T15:29:22.493 300.0 5 14.85
10 18:23:19.201 +16:08:60.00 2019-05-21T15:37:16.618 240.0 4 13.47
11 18:01:16.799 +11:03:00.00 2019-05-21T15:45:37.945 300.0 5 14.83
12 19:01:14.401 +22:57:00.00 2019-05-21T15:52:45.649 300.0 5 15.20

The covering map is available at:
http://cmm.svom.cn/gwpub/O3/S190521r/S190521r_GWAC-F30.png
(user:svomo3 pwd:gwo3)

The first image was taken ~7.3 hours after the event trigger time. The
weather conditions were partly cloudy during the night. 
No credible new source is detected by our online pipeline.
A more detailed image analysis is in progress with our offline pipeline
to search for any fainter transient candidate.