GCN Circular 21789

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