TITLE: GCN CIRCULAR NUMBER: 26509 SUBJECT: LIGO/Virgo S191216ap: Subaru/Hyper Suprime-Cam observations of GW+IceCube+HAWC error region DATE: 19/12/20 07:26:15 GMT FROM: Takayuki Ohgami at Konan University T. Ohgami, N. Tominaga (Konan U.), R. Ohsawa, Y. Niino, T. Morokuma (U. Tokyo), T. Terai, Y. Takagi, K. Yanagisawa, M. Yoshida (NAOJ), M. Sasada (Hiroshima U.), M. Tanaka (Tohoku U.), Y. Sekiguchi (Toho U.), Y. Utsumi (Stanford/SLAC) on behalf of J-GEM collaboration Following detections of S191216ap by LIGO-Virgo (Piotrzkowski et al., GCN Circ. 26454, 26505) and possible related events by IceCube (Hussain et al., CGN Circ. 26460) and by HAWC (Martinez-Castellano et al., GCN Circ. 26472), we selected a galaxy, GL213356+051647 (ra, dec = 323.4824, 5.2796 at 274.42 Mpc), from our candidate selection algorithm based on the GLADE v2.3 catalog (Dalya et al., 2018) and the localization maps. Our candidate galaxy is also ranked as the top candidate in Singer et al. (GCN Circ. 26479). Using a 1.5 deg circular aperture of Subaru/Hyper Suprime-Cam which covers the HAWC's 68% credible region, we imaged a region around GL213356+051647 with an integration time of 2730 sec for z-band, starting from 2019-12-20 05:06 UT. An estimated limiting magnitude is 25.5. We found no apparent transient associated with GL213356+051647. More detailed analysis is ongoing, and further follow-up observations are planned. We thank Subaru's staff for making this observation.