GCN Circular 24136

X.H. Han (NAOC), J.Y. Wei (NAOC), C. Wu (NAOC), L.P. Xin (NAOC),
D. Turpin (NAOC), N. LEROY (CNRS/LAL), S. ANTIER (CNRS/APC/CNES),
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. Gotz (CEA/AIM), A. Claret (CEA/AIM), C. Lachaud (CNRS/APC),
R. Duque (CNRS/IAP), N. Dagoneau (CEA/AIM) S.N. Zhang (IHEP),
B.B. Wu (IHEP),
report on behalf of the SVOM Ground Follow-up Group:


We observed 7 sky regions (total: 1100 square degrees) to cover the
skymap of the advanced LIGO/Virgo trigger S190412M, 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 15 seconds (10s exposure + 5s readout).
We estimate a 95% prior probability that these 7 regions contain the
true location of the source.
The coordinates of the 7 regions and observation time are list following:

No. Ra Dec start-obs(UTC) end-obs(UTC) Telescope_ID
1 12:16:08.501 +13:42:34.43 2019-04-12 14:21:03 2019-04-12 14:53:31 2
2 13:04:12.375 +13:07:23.42 2019-04-12 14:21:03 2019-04-12 14:53:31 2
3 13:01:14.699 +01:23:57.03 2019-04-12 14:21:03 2019-04-12 14:53:31 2
4 14:15:50.897 +35:59:33.54 2019-04-12 14:05:51 2019-04-12 14:20:11 2
5 15:42:30.509 +35:59:41.27 2019-04-12 14:05:51 2019-04-12 14:20:11 2
6 12:16:49.785 +01:39:44.92 2019-04-12 14:21:03 2019-04-12 14:53:31 2
7 14:47:20.959 +36:20:07.37 2019-04-12 14:05:51 2019-04-12 14:20:11 2

The covering map is available at:
http://cmm.svom.cn/gwpub/O3/S190412m/S190412m_GWAC.png
(user:svomo3 pwd:gwo3)

The first image was taken ~8 hours after the event trigger time. The
weather conditions were bad (cloudy) during the observations. A 3
sigma limiting magnitude of about 14 mag in R band is obtained in
our single frames. No credible new source is detected by our online
pipeline.
A more detailed image analysis including co-addition is ongoing with
our offline pipeline to search for transient candidates.

This circular is citable.