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 <youtsumi@hiroshima-u.ac.jp> 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 ----------------------------------