[vsnet-grb-info 22559] LIGO/Virgo S190521g: No optical counterpart from SVOM/GWAC-F30 observations.

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  24658
SUBJECT: LIGO/Virgo S190521g: No optical counterpart from SVOM/GWAC-F30 observations.
DATE:    19/05/24 11:43:41 GMT
FROM:    Damien Turpin at NAOC (CAS)  <dturpin-astro at hotmail.com>

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 4 sky regions to cover the initial skymap of the 
LIGO/Virgo trigger S190521g (GCN24621), 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 4 tile coordinates and the observation periods are listed below:

# Ra[hms] Dec[dms] start-obs[UTC] Total_exp[s] N_image R_lim
1 12:33:04.799 +28:03:00.00 2019-05-21T13:53:59.727 300.0 5 16.82
2 16:40:40.800 +45:03:00.00 2019-05-21T14:02:19.437 300.0 5 16.33
3 16:41:33.601 +46:45:00.00 2019-05-21T13:19:33.245 300.0 5 16.38
4 16:50:12.239 +45:03:39.96 2019-05-21T13:16:11.066 420.0 7 15.75

The covering map is available at:
http://cmm.svom.cn/gwpub/O3/S190521g/S190521g_GWAC-F30.png
(user:svomo3 pwd:gwo3)

The first image was taken ~10.8 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.