TITLE: GCN CIRCULAR NUMBER: 21549 SUBJECT: LIGO/Virgo G298048: Subaru HSC follow-up observations DATE: 17/08/18 07:07:07 GMT FROM: Yousuke Utsumi at Hiroshima Astrophys. Science Center Yoshida, M., Tanaka, M., Terai, T., Nakata, F., Furusawa, H., Koshida, S. (NAOJ), Utsumi, Y., Kawabata K. S. (Hiroshima Univ.), Tominaga, N. (Konan Univ.), Motohara, K., Ohsawa, R., Morokuma, T. (Univ. of Tokyo), Kawai, N. (Tokyo Tech) on behalf of the J-GEM collaboration We performed follow-up observations for the gravitational event G298048 (GCN 21505; 21509; 21513) with Hyper Suprime-Cam attached to the Subaru telescope on August 18 2017 UT. The observations started at 5:20 UT and were continued until 6:00 UT. We used HSC-z band filter. The sky area of about 25 deg2 centered at (alpha, delta) = (-162.8 deg, -25 deg) was covered with 24 HSC pointings. This area includes the candidate of optical counterpart (SSS17a) in the galaxy NGC 4993 reported by Coulter et al. (GCN 21529) and covers 60% of the probability area of the LALInference skymap (GCN 21527). Typical exposure time was 30 seconds. SSS17a is clearly seen in our z-band images. We made rough photometry of this object and obtained z-band magnitude of ~17 (AB). Further analysis is on going. The sky fields and galaxies observed by this survey are listed below: ID Time RA DEC Exp Filter ----------------------------------------------------------- 28 2017-08-18T05:08:43 13h10m22.9s -23d18m49.1s 2.0s HSC-z 28 2017-08-18T05:12:13 13h10m22.9s -23d18m49.0s 2.0s HSC-z 28 2017-08-18T05:15:23 13h10m22.9s -23d18m49.1s 2.0s HSC-z 28 2017-08-18T05:16:25 13h10m22.9s -23d18m49.0s 2.0s HSC-z 28 2017-08-18T05:20:04 13h10m22.9s -23d18m49.0s 2.0s HSC-z 04 2017-08-18T05:21:18 13h07m34.2s -26d36m20.9s 5.0s HSC-z 28 2017-08-18T05:22:43 13h10m14.4s -23d19m20.0s 1.2s HSC-z 28 2017-08-18T05:25:56 13h10m14.5s -23d19m20.2s 1.2s HSC-z 28 2017-08-18T05:30:27 13h10m14.4s -23d19m20.1s 20.0s HSC-z 05 2017-08-18T05:32:00 13h10m23.0s -27d16m31.1s 30.0s HSC-z 06 2017-08-18T05:33:00 13h13m11.8s -27d56m56.0s 30.0s HSC-z 07 2017-08-18T05:34:03 13h16m00.6s -28d37m36.1s 30.0s HSC-z 08 2017-08-18T05:35:03 13h18m49.3s -29d18m32.0s 30.0s HSC-z 09 2017-08-18T05:36:03 13h21m38.1s -29d59m44.5s 30.0s HSC-z 10 2017-08-18T05:37:09 13h04m45.4s -24d37m11.8s 30.0s HSC-z 11 2017-08-18T05:38:10 13h07m34.2s -25d16m41.8s 30.0s HSC-z 12 2017-08-18T05:39:10 13h10m22.9s -25d56m24.5s 30.0s HSC-z 28 2017-08-18T05:40:10 13h10m22.9s -23d18m48.9s 60.0s HSC-z 13 2017-08-18T05:41:41 13h13m11.7s -26d36m21.0s 30.0s HSC-z 14 2017-08-18T05:42:42 13h01m56.6s -22d39m54.9s 30.0s HSC-z 15 2017-08-18T05:43:45 13h16m00.5s -27d16m31.1s 30.0s HSC-z 16 2017-08-18T05:44:46 13h18m49.3s -27d56m55.9s 30.0s HSC-z 17 2017-08-18T05:45:50 13h04m45.4s -23d18m48.9s 30.0s HSC-z 18 2017-08-18T05:46:51 13h07m34.1s -23d57m54.5s 30.0s HSC-z 19 2017-08-18T05:47:52 12h59m07.8s -20d44m16.9s 30.0s HSC-z 20 2017-08-18T05:48:54 13h10m22.9s -24d37m12.1s 30.0s HSC-z 22 2017-08-18T05:49:55 13h13m11.7s -25d16m41.9s 30.0s HSC-z 23 2017-08-18T05:50:55 13h16m00.4s -25d56m24.5s 30.0s HSC-z 24 2017-08-18T05:52:05 12h56m19.0s -18d50m06.2s 30.0s HSC-z 25 2017-08-18T05:53:09 13h04m45.3s -22d01m12.0s 30.0s HSC-z 26 2017-08-18T05:54:11 13h07m34.1s -22d39m55.1s 30.0s HSC-z 29 2017-08-18T05:55:16 13h01m56.5s -20d06m04.1s 30.0s HSC-z ----------------------------------------------------------- # observed galaxy list Name RA DEC -------------------------------- GL125437-181830 193.6546 -18.3082 GL125600-191608 193.9987 -19.269 GL125703-193105 194.261 -19.5181 GL125812-210245 194.55 -21.046 GL130407-250220 196.031 -25.0388 GL130415-225252 196.063 -22.8812 GL130505-222302 196.2706 -22.3839 GL130524-233121 196.348 -23.5226 GL130525-233009 196.354 -23.5025 GL130619-225849 196.5808 -22.9803 GL130624-240950 196.6001 -24.164 GL130640-222721 196.6664 -22.4558 GL130653-225030 196.719 -22.8418 GL130657-235501 196.7355 -23.9171 GL130706-234037 196.7749 -23.677 GL130708-240641 196.782 -24.1114 GL130731-231014 196.879 -23.1705 GL130734-234855 196.892 -23.8152 GL130734-240031 196.8906 -24.0086 GL130738-233444 196.9072 -23.5789 GL130738-235618 196.907 -23.9384 GL130745-225128 196.937 -22.8578 GL130804-234749 197.018 -23.7968 GL130832-232050 197.135 -23.3472 GL130842-234633 197.177 -23.7757 GL130842-242258 197.175 -24.3828 GL130918-242255 197.324 -24.3821 GL130919-242304 197.329 -24.3846 GL130948-232302 197.4488 -23.3838 GL130952-241422 197.466 -24.2394 GL130952-241424 197.465 -24.24 GL131000-234253 197.4993 -23.7146 GL131001-264243 197.504 -26.7118 GL131007-263543 197.529 -26.5953 GL131023-275837 197.595 -27.977 GL131046-235157 197.6914 -23.8657 GL131110-280037 197.79 -28.0103 GL131247-255912 198.195 -25.9866 GL131406-290116 198.5231 -29.0212 GL131418-263458 198.5739 -26.5827 GL131427-271243 198.611 -27.212 GL131531-281703 198.8771 -28.2841 GL131608-282438 199.0349 -28.4105 GL131610-291131 199.04 -29.192 GL131611-283941 199.0473 -28.6613 GL131616-292111 199.0658 -29.353 GL131618-292642 199.0742 -29.4449 GL131620-281709 199.0837 -28.2857 GL131623-263342 199.0968 -26.5616 GL131645-275310 199.189 -27.8861 GL131651-283105 199.2137 -28.5181 GL131657-252015 199.239 -25.3375 GL131748-265409 199.45 -26.9025 GL131752-264748 199.465 -26.7966 GL131805-265014 199.5211 -26.8372 GL131824-272606 199.6 -27.435 GL131901-273743 199.7522 -27.6285 GL131939-284424 199.9116 -28.7401 GL131941-272544 199.919 -27.429 GL131950-272436 199.9584 -27.4101 GL132014-300209 200.058 -30.036 GL132045-302028 200.188 -30.341 GL132050-292847 200.2091 -29.4798 GL132109-303927 200.2879 -30.6575 GL132208-304240 200.532 -30.7112 GL132218-300915 200.575 -30.1543 GL132324-293551 200.8513 -29.5976 GL132331-300651 200.8777 -30.1143 GL132343-300324 200.9291 -30.0568 GL132414-301522 201.06 -30.256 GL132425-301505 201.1048 -30.2514 GL132428-302555 201.1148 -30.4319 ----------------------------------