TITLE: GCN CIRCULAR NUMBER: 27205 SUBJECT: LIGO/Virgo S200224ca: Subaru/Hyper Suprime-Cam follow-up observations DATE: 20/02/25 16:17:36 GMT FROM: Takayuki Ohgami at Konan University T. Ohgami, N. Tominaga (Konan U.), T. Morokuma (U. Tokyo), T. Terai, Y. Takagi, K. Yanagisawa, M. Yoshida (NAOJ), H. Onozato (U. Hyogo), M. Sasada (Hiroshima U.), M. Tanaka (Tohoku U.), Y. Utsumi (Stanford/SLAC), on behalf of J-GEM collaboration We report optical follow-up observations for a high probability area of S200224ca (LIGO Scientific Collaboration and the Virgo Collaboration, GCN #27184) with Hyper Suprime-Cam (HSC) attached to 8.2-m Subaru Telescope. Subaru/HSC has a circular field-of-view of 1.7 deg^2. We performed HSC-r2 and HSC-z band imaging observations on 2020-02-25 UT. We start the first exposure at 10:43 UT, which corresponds to 12.3 hours after the GW detection. The exposure time per frame was 30 sec. We covered 82.5% of probability region with 60 pointings of the HSC. We revisited each pointing twice in each band. The estimated limiting magnitudes in HSC-r2 and HSC-z band are about 24.8 mag and 23.5 mag, respectively. Detailed analysis is ongoing, and further follow-up observations are planned. We thank Subaru's staff for making this observation. The central coordinates of the observed regions are as follows: JGEM30716 11:40:18.75 -14:28:39.0 JGEM29691 11:34:41.25 -12:01:28.9 JGEM28923 11:31:52.50 -10:11:59.7 JGEM30973 11:43:07.50 -15:05:41.2 JGEM29948 11:37:30.00 -12:38:08.3 JGEM28154 11:29:03.75 -08:23:07.9 JGEM29179 11:34:41.25 -10:48:24.9 JGEM30204 11:40:18.75 -13:14:52.9 JGEM28411 11:31:52.50 -08:59:21.5 JGEM30461 11:43:07.50 -13:51:43.0 JGEM29436 11:37:30.00 -11:24:54.6 JGEM27642 11:29:03.75 -07:10:50.7 JGEM26874 11:26:15.00 -05:22:45.8 JGEM28667 11:34:41.25 -09:35:38.6 JGEM30717 11:45:56.25 -14:28:39.0 JGEM29692 11:40:18.75 -12:01:28.9 JGEM27899 11:31:52.50 -07:46:57.8 JGEM30974 11:48:45.00 -15:05:41.2 JGEM28924 11:37:30.00 -10:11:59.7 JGEM29949 11:43:07.50 -12:38:08.3 JGEM27130 11:29:03.75 -05:58:45.0 JGEM26362 11:26:15.00 -04:10:53.5 JGEM28155 11:34:41.25 -08:23:07.9 JGEM30205 11:45:56.25 -13:14:52.9 JGEM29180 11:40:18.75 -10:48:24.9 JGEM27387 11:31:52.50 -06:34:46.5 JGEM26618 11:29:03.75 -04:46:48.7 JGEM28412 11:37:30.00 -08:59:21.5 JGEM30462 11:48:45.00 -13:51:43.0 JGEM29437 11:43:07.50 -11:24:54.6 JGEM25850 11:26:15.00 -02:59:07.8 JGEM27643 11:34:41.25 -07:10:50.7 JGEM30718 11:51:33.75 -14:28:39.0 JGEM28668 11:40:18.75 -09:35:38.6 JGEM29693 11:45:56.25 -12:01:28.9 JGEM26875 11:31:52.50 -05:22:45.8 JGEM26106 11:29:03.75 -03:34:60.0 JGEM27900 11:37:30.00 -07:46:57.8 JGEM29950 11:48:45.00 -12:38:08.3 JGEM28925 11:43:07.50 -10:11:59.7 JGEM27131 11:34:41.25 -05:58:45.0 JGEM26363 11:31:52.50 -04:10:53.5 JGEM28156 11:40:18.75 -08:23:07.9 JGEM30206 11:51:33.75 -13:14:52.9 JGEM29181 11:45:56.25 -10:48:24.9 JGEM27388 11:37:30.00 -06:34:46.5 JGEM28413 11:43:07.50 -08:59:21.5 JGEM29438 11:48:45.00 -11:24:54.6 JGEM26619 11:34:41.25 -04:46:48.7 JGEM25851 11:31:52.50 -02:59:07.8 JGEM27644 11:40:18.75 -07:10:50.7 JGEM29694 11:51:33.75 -12:01:28.9 JGEM28669 11:45:56.25 -09:35:38.6 JGEM26876 11:37:30.00 -05:22:45.8 JGEM26107 11:34:41.25 -03:34:60.0 JGEM27901 11:43:07.50 -07:46:57.8 JGEM28926 11:48:45.00 -10:11:59.7 JGEM27132 11:40:18.75 -05:58:45.0 JGEM28157 11:45:56.25 -08:23:07.9 JGEM27389 11:43:07.50 -06:34:46.5