TITLE: GCN CIRCULAR NUMBER: 21789 SUBJECT: LIGO/Virgo G297595: DECam observations of BBH merger region of interest DATE: 17/09/02 21:33:18 GMT FROM: M. Soares-Santos at Fermi Lab S. Allam (Fermilab), J. Annis (Fermilab), J.Garcia Bellido (IFT CSIC/UAM), E. Berger (Harvard), D. J. Brout (UPenn), D. Brown (Syracuse), R. E. Butler (Fermilab), H.-Y. Chen (Harvard), R. Chornock (Ohio University), E. Cook (TAMU), P. S. Cowperthwaite (Harvard), H. T. Diehl (Fermilab), A. Drlica-Wagner (Fermilab), Z. Doctor (U. Chicago), M. R. Drout (Carnegie), B. Farr (U Chicago), R. J. Foley (UCSC), W. Fong (Northwestern), D. Fox (Penn State), J. Frieman (Fermilab/UChicago), M.S.S. Gill (Stanford), R. Gruendl (NCSA), K. Herner (Fermilab), D. Holz (UChicago), R. Kessler (UChicago), H. Lin (Fermilab), J. Marriner (Fermilab), R. Margutti (Northwestern), J. Marshall (TAMU), E. Neilsen (Fermilab), F. Paz-Chincon (NCSA), M. Nicholl (Harvard), A. Rest (STScI), M. Sako (UPenn), D. Scolnic (KICP), N. Smith (Arizona), M. Soares-Santos (BrandeisU), D. Tucker (Fermilab), V. A. Villar (Harvard), A. Walker (NOAO), B. Yanny (Fermilab), P. K. G. Williams (Harvard) On behalf of the DESGW+community team: We report on observations of LVC trigger G297595 conducted with the Dark Energy camera (DECam) on the Blanco 4-m telescope at CTIO (program 2017B-0110, PI: Berger) for several nights starting on 2017-08-15 UT. Observations consisted of 90 second exposures in i band. On the first night observations started at 2017-08-15 06:00 UT (19 hours after the GW detection). In 4 hours of observing time we performed two tilings of the area and covered 90% of the localization probability given by the LVC sky map available at the time. On the second night observations started at 2017-08-16 06:00 UT. We performed a second visit of the area covered in the previous night. At 07:02 UT a new map was released by LVC. Our observations overlapped 49% of the probability on the new map. We recomputed our sky footprint and, at 08:11 UT, started observations covering a total of 84% of the new localization probability. On the third night we performed a second tiling of the new area starting at 2017-08-17 06:30 UT. We revisited the new area 4 more times. The last visit of the region was on the night of 2017-08-26 UT. DECam has a 3 sq-deg field of view and typically reaches i,z = 23rd limiting magnitudes for 90 second exposures. We have covered 160 sq-deg, corresponding to 84% of the updated localization probability, to 23rd mag in i band. The table below lists the coordinates observed (first epoch only). Data reduction is being performed using the DES software pipeline and an independent pipeline on the Harvard Odyssey computer cluster. Difference imaging is being performed using pre-existing DES exposures as templates. Analysis is underway. 108 rows returned expnumradecairmassseeingmag_limtime_since_trigger 667113 33.081017 -53.7447 1.36 1.131 22.70 19:29:38.500579 667114 34.526567 -47.6579 1.35 1.164 22.70 19:31:49.617109 667115 34.908854 -45.6289 1.35 1.232 22.64 19:33:49.704425 667116 37.8198 -40.5565 1.39 1.496 22.41 19:35:57.406561 667117 40.14195 -37.5131 1.43 1.4 22.46 19:37:56.378284 667118 41.501492 -50.7013 1.43 1.16 22.64 19:40:27.438763 667120 44.232871 -31.4262 1.52 1.179 22.59 19:45:04.830179 667121 46.071733 -28.3827 1.58 1.174 22.59 19:47:04.174300 667122 46.098692 -30.4117 1.55 1.118 22.66 19:49:01.944646 667123 46.386629 -44.6144 1.47 1.143 22.68 19:51:35.334292 667125 47.925883 -29.3972 1.56 1.312 22.46 19:56:11.468952 667126 47.993579 -31.4262 1.53 1.311 22.48 19:58:09.701798 667127 48.068325 -33.4551 1.5 1.323 22.46 20:00:09.554130 667128 48.151142 -35.4841 1.48 1.325 22.48 20:02:08.778424 667129 48.242654 -37.5131 1.46 1.252 22.56 20:04:07.371388 667130 48.343783 -39.542 1.45 1.194 22.59 20:06:06.372826 667131 42.266758 -34.4696 1.34 1.178 22.66 20:08:17.035111 667132 47.864804 -27.3683 1.48 1.222 22.54 20:10:30.827879 667133 33.620458 -51.7158 1.24 1.084 22.84 20:13:27.625683 667134 34.099333 -49.6868 1.23 1.049 22.89 20:15:26.147706 667135 36.02235 -52.7303 1.26 1.139 22.77 20:17:26.087003 667136 37.345425 -44.6144 1.23 1.516 22.48 20:19:48.078520 667137 37.594904 -42.5855 1.22 1.292 22.63 20:21:46.394679 667138 38.82525 -51.7158 1.26 1.175 22.73 20:24:09.877128 667139 39.859292 -41.571 1.24 1.205 22.68 20:26:33.378343 667140 40.007792 -39.542 1.23 1.127 22.77 20:28:32.514268 667141 42.130425 -38.5275 1.25 1.144 22.73 20:30:32.596601 667142 42.202033 -36.4986 1.25 1.076 22.81 20:32:32.148424 667143 44.089667 -47.6579 1.27 1.141 22.75 20:34:59.845293 667145 44.220629 -33.4551 1.25 1.242 22.64 20:39:28.326716 667146 46.12845 -32.4407 1.28 1.175 22.69 20:41:26.347140 667147 46.161358 -34.4696 1.26 1.135 22.73 20:43:27.175973 667148 46.197842 -36.4986 1.26 1.11 22.81 20:45:26.086710 667149 46.282604 -40.5565 1.25 1.065 22.83 20:47:28.378746 667150 46.331908 -42.5855 1.25 1.08 22.85 20:49:27.419364 667151 44.207146 -35.4841 1.21 0.952 22.96 20:51:56.583169 667153 36.758192 -48.6723 1.16 0.996 22.95 20:56:32.782815 667154 37.067833 -46.6434 1.15 0.97 22.97 20:58:31.339136 667155 39.080533 -49.6868 1.18 0.987 22.93 21:00:30.766293 667156 39.308158 -47.6579 1.16 0.984 22.97 21:02:28.452052 667157 39.511846 -45.6289 1.15 1.051 22.89 21:04:27.301000 667158 39.694696 -43.5999 1.14 1.112 22.83 21:06:25.419905 667159 41.636792 -48.6723 1.17 1.105 22.83 21:08:36.460086 667160 41.757629 -46.6434 1.16 1.01 22.91 21:10:34.758344 667161 41.866021 -44.6144 1.15 1.019 22.92 21:12:33.041454 667162 41.9634 -42.5855 1.14 0.992 22.94 21:14:31.312051 667163 42.051196 -40.5565 1.13 1.011 22.90 21:16:30.358284 667164 44.114746 -45.6289 1.16 1.007 22.92 21:18:37.993401 667165 44.137292 -43.5999 1.15 0.942 22.97 21:20:37.989628 667166 44.157496 -41.571 1.14 1.022 22.88 21:22:36.577622 667167 44.175796 -39.542 1.13 1.101 22.80 21:24:36.200377 667168 44.19225 -37.5131 1.13 1.04 22.88 21:26:35.962091 667169 46.238025 -38.5275 1.14 1.035 22.88 21:28:33.252666 667170 46.238025 -38.5275 1.14 1.042 22.86 21:30:33.628407 667637 36.02235 -52.7303 1.12 1.374 22.64 1 day, 21:41:03.836806 667638 36.411796 -50.7013 1.1 1.19 22.80 1 day, 21:43:01.770738 667639 36.758192 -48.6723 1.09 1.1 22.88 1 day, 21:44:59.834221 667640 37.067833 -46.6434 1.08 1.137 22.84 1 day, 21:46:58.881032 667641 38.537821 -53.7447 1.13 1.022 22.92 1 day, 21:49:14.047259 667642 39.511846 -45.6289 1.08 0.954 23.01 1 day, 21:51:35.282434 667643 39.694696 -43.5999 1.07 0.919 23.05 1 day, 21:53:32.996321 667644 41.349346 -52.7303 1.12 1.049 22.91 1 day, 21:55:58.142319 667645 41.9634 -42.5855 1.07 0.999 22.98 1 day, 21:58:24.355336 667646 44.175796 -39.542 1.07 0.949 23.05 1 day, 22:00:25.022154 667647 46.197842 -36.4986 1.07 1.018 22.99 1 day, 22:02:23.856376 667648 46.591183 -50.7013 1.12 1.138 22.84 1 day, 22:04:55.598562 667649 48.068325 -33.4551 1.07 1.033 22.94 1 day, 22:07:36.909732 667650 49.818992 -30.4117 1.08 1.013 22.95 1 day, 22:09:35.571894 667651 51.475817 -27.3683 1.09 1.035 22.92 1 day, 22:11:34.892573 667652 50.907329 -44.6144 1.1 1.151 22.84 1 day, 22:14:14.888743 667653 52.292954 -37.5131 1.09 1.103 22.89 1 day, 22:16:34.033753 667654 52.511683 -39.542 1.09 1.205 22.78 1 day, 22:18:32.990654 667655 38.82525 -51.7158 1.09 1.21 22.78 1 day, 22:21:07.325116 667656 39.080533 -49.6868 1.07 1.127 22.89 1 day, 22:23:05.824461 667657 39.308158 -47.6579 1.06 1.211 22.80 1 day, 22:25:03.367628 667658 41.501492 -50.7013 1.08 1.173 22.84 1 day, 22:27:03.333138 667659 41.636792 -48.6723 1.07 1.194 22.82 1 day, 22:29:01.859464 667660 41.757629 -46.6434 1.06 1.128 22.90 1 day, 22:30:59.623472 667661 41.866021 -44.6144 1.05 1.032 23.00 1 day, 22:32:57.799484 667662 44.030158 -51.7158 1.09 1.181 22.83 1 day, 22:35:36.632387 667663 44.157496 -41.571 1.04 1.062 22.94 1 day, 22:38:02.053494 667664 46.238025 -38.5275 1.03 1.125 22.91 1 day, 22:40:01.143328 667665 48.151142 -35.4841 1.03 1.04 22.95 1 day, 22:42:00.345576 667666 48.871258 -47.6579 1.07 1.082 22.91 1 day, 22:44:27.561412 667667 49.93155 -32.4407 1.03 1.047 22.97 1 day, 22:47:02.461422 667668 50.700404 -42.5855 1.05 1.039 22.97 1 day, 22:49:24.916068 667669 51.607892 -29.3972 1.03 1.071 22.92 1 day, 22:51:55.034195 667670 51.754275 -31.4262 1.03 1.071 22.94 1 day, 22:53:54.540442 667671 51.916125 -33.4551 1.03 1.155 22.86 1 day, 22:55:53.947934 667672 52.095046 -35.4841 1.03 1.091 22.96 1 day, 22:57:53.351123 667673 44.061646 -49.6868 1.07 1.16 22.88 1 day, 23:01:06.555281 667674 44.089667 -47.6579 1.05 1.151 22.88 1 day, 23:03:04.628618 667675 44.114746 -45.6289 1.04 1.135 22.89 1 day, 23:05:04.104997 667676 44.137292 -43.5999 1.03 1.16 22.86 1 day, 23:07:02.134092 667677 46.282604 -40.5565 1.02 1.139 22.91 1 day, 23:09:01.550370 667678 46.331908 -42.5855 1.03 1.207 22.84 1 day, 23:10:59.205759 667679 46.386629 -44.6144 1.04 1.294 22.77 1 day, 23:12:57.317365 667680 46.447529 -46.6434 1.05 1.258 22.81 1 day, 23:14:56.838481 667681 46.5153 -48.6723 1.06 1.339 22.73 1 day, 23:16:54.491556 667682 48.242654 -37.5131 1.01 1.423 22.69 1 day, 23:19:19.875913 667683 48.343783 -39.542 1.02 1.204 22.86 1 day, 23:21:19.338861 667684 48.455683 -41.571 1.02 1.166 22.91 1 day, 23:23:17.317086 667685 48.5799 -43.5999 1.03 1.237 22.83 1 day, 23:25:16.075497 667686 48.71775 -45.6289 1.04 1.19 22.85 1 day, 23:27:14.313076 667687 50.05605 -34.4696 1.01 1.143 22.92 1 day, 23:29:40.767316 667688 50.193629 -36.4986 1.01 1.28 22.80 1 day, 23:31:40.215267 667689 50.345717 -38.5275 1.01 1.177 22.89 1 day, 23:33:38.757192 667690 50.514 -40.5565 1.02 1.062 23.00 1 day, 23:35:36.910088