TITLE: GCN CIRCULAR NUMBER: 26571 SUBJECT: LIGO/Virgo S191222n: no counterpart candidate in SVOM/GWAC observations DATE: 19/12/24 02:40:16 GMT FROM: Xuhui Han at NAOC/SVOM C. Wu (NAOC), M. Dennefeld (IAP/CNRS/SU) , X. Wang (GXU), R. Duque (CNRS/IAP), S.S. Sun (GXU) report on behalf of the SVOM Multi Messenger Astronomy and GWAC teams (http://www.svom.fr/en/svom-mma-and-gwac-team ): We observed 37 150-sq. deg sky regions to cover the skymap of the advanced LIGO/Virgo trigger S191222n (GCN # 26543), with SVOM/GWAC, at Xinglong Observatory. SVOM/GWAC is equipped with two sets of wide angle cameras: - FFOV cameras (FOV~900 square degrees/camera, aperture = 3.5 cm), - JFOV cameras (FOV~150 square degrees/camera, aperture = 18 cm). SVOM/GWAC currently comprises 4 FFOV cameras and 16 JFOV cameras, working in the unfiltered band. The observations are operated in time-series mode, taking one exposure every 25 seconds (20s exposure + 5s readout). The observed and processed regions enclosed an estimated 36.9% of the probability of the advanced LIGO/Virgo skymap. Images were taken between ~8.8 minutes and ~16.63 hours after the GW trigger time. The coordinates of the 37 sky regions observed after the trigger and their observation times and covered probability are listed below: Id Ra Dec start (UTC) end (UTC) Cov. Cam. 1 07:24:00.24 53:02:52.80 2019-12-22 12:32:11 2019-12-22 12:59:41 0.021 JFOV 2 05:50:52.75 52:05:58.20 2019-12-22 12:17:05 2019-12-22 12:23:10 0.029 JFOV 3 07:30:30.00 48:26:49.56 2019-12-22 13:37:33 2019-12-22 14:39:54 0.017 JFOV 4 08:31:26.64 36:09:36.36 2019-12-22 13:41:12 2019-12-22 14:39:54 0.001 JFOV 5 08:26:42.72 47:40:49.80 2019-12-22 13:28:55 2019-12-22 13:49:59 0.017 JFOV 6 08:57:33.12 48:28:44.40 2019-12-22 14:40:49 2019-12-22 15:08:43 0.014 JFOV 7 09:58:28.80 36:10:45.48 2019-12-22 14:40:49 2019-12-22 15:08:44 0.010 JFOV 8 09:03:17.76 36:28:34.68 2019-12-22 14:40:49 2019-12-22 15:08:44 0.005 JFOV 9 09:53:40.32 47:42:14.40 2019-12-22 14:56:46 2019-12-22 15:41:54 0.004 JFOV 10 08:46:46.08 35:05:22.92 2019-12-22 14:41:22 2019-12-22 15:41:54 0.001 JFOV 11 11:07:09.36 14:33:39.96 2019-12-22 17:28:48 2019-12-22 17:56:42 0.008 JFOV 12 11:52:22.32 02:14:49.49 2019-12-22 17:28:48 2019-12-22 17:56:43 0.024 JFOV 13 11:43:29.28 13:47:45.24 2019-12-22 17:28:23 2019-12-22 17:56:20 0.011 JFOV 14 11:43:07.44 01:33:46.40 2019-12-22 17:28:23 2019-12-22 17:55:56 0.017 JFOV 15 13:05:04.80 -14:43:42.60 2019-12-22 19:55:37 2019-12-22 20:13:24 0.059 JFOV 16 12:19:09.84 -14:28:44.04 2019-12-22 19:45:30 2019-12-22 20:13:24 0.029 JFOV 17 12:54:54.96 -3:11:46.03 2019-12-22 19:45:37 2019-12-22 20:13:35 0.015 JFOV 18 01:16:50.26 13:21:14.40 2019-12-22 10:55:10 2019-12-22 10:56:23 0.002 JFOV 19 01:31:43.61 -2:38:38.15 2019-12-22 12:00:30 2019-12-22 12:28:24 0.011 JFOV 20 01:31:11.11 -14:41:56.76 2019-12-22 12:00:30 2019-12-22 12:28:25 0.003 JFOV 21 01:15:33.36 -15:41:16.80 2019-12-22 12:32:50 2019-12-22 13:00:47 0.002 JFOV 22 02:22:18.02 19:03:32.04 2019-12-22 11:36:09 2019-12-22 11:56:47 0.039 JFOV 23 01:35:19.34 19:18:38.16 2019-12-22 11:51:07 2019-12-22 11:56:47 0.004 JFOV 24 01:20:10.46 18:12:47.16 2019-12-22 11:34:30 2019-12-22 11:57:11 0.001 JFOV 25 02:48:12.86 31:22:33.96 2019-12-22 10:12:47 2019-12-22 10:39:04 0.047 JFOV 26 03:43:25.08 30:52:54.84 2019-12-22 10:26:10 2019-12-22 10:28:04 0.012 JFOV 27 02:50:44.57 19:20:33.36 2019-12-22 10:19:15 2019-12-22 10:39:04 0.021 JFOV 28 02:33:21.58 30:19:24.96 2019-12-22 10:10:30 2019-12-22 10:38:27 0.037 JFOV 29 03:28:18.70 18:23:05.64 2019-12-22 10:16:10 2019-12-22 10:38:27 0.022 JFOV 30 02:35:25.70 18:14:51.72 2019-12-22 10:11:43 2019-12-22 10:38:27 0.032 JFOV 31 05:29:11.35 53:00:20.88 2019-12-22 13:03:21 2019-12-22 13:31:15 0.032 JFOV 32 04:15:03.79 53:17:51.36 2019-12-22 13:03:45 2019-12-22 13:23:58 0.019 JFOV 33 04:36:43.78 48:22:15.60 2019-12-22 11:11:19 2019-12-22 11:25:29 0.039 JFOV 34 04:42:32.40 36:22:20.28 2019-12-22 11:14:09 2019-12-22 11:20:13 0.002 JFOV 35 04:20:09.24 47:15:37.80 2019-12-22 11:16:02 2019-12-22 11:27:22 0.042 JFOV 36 05:32:53.42 47:36:12.96 2019-12-22 11:10:51 2019-12-22 11:25:51 0.024 JFOV 37 04:26:06.91 35:13:31.80 2019-12-22 10:57:54 2019-12-22 11:24:14 0.003 JFOV The sky coverage map is available at: http://cmm.svom.cn/gwpub/O3/S191222n/S191222n.png (user:svomo3 pwd:gwo3). Weather conditions were clear during the observations. An average 3-sigma limiting magnitude of 16 mag in the R band was obtained in the single frames. No credible new source was 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.