GCN Circular 18350

M. Soares-Santos (Fermilab), J. Annis (Fermilab), E. Berger (Harvard),
D. J. Brout (UPenn), H.-Y. Chen (UChicago), P. Cowperthwaite (Harvard),
H. T. Diehl (Fermilab), B. Farr (UChicago), D. A. Finley (Fermilab), J.
Frieman (Fermilab/UChicago), M. Garcia (CIEMAT/Madrid), R. Gruendl
(NCSA), D. Hollowood (UCSC), D. Holz (UChicago), R. Kessler (UChicago),
A. Kim (LBNL), K. Herner (Fermilab), E. Neilsen (Fermilab), M. Sako
(UPenn), B. Yanny (Fermilab)
On behalf of the DESGW team:

We report on observations done with the Dark Energy camera (DECam) on
the Blanco telescope at CTIO on the night of 2015-09-18 in response to
the LVC trigger G184098. These observations complement those taken on
2015-09-17, increasing the area coverage by about 20%.�� Our
observations were delayed by 1 night due to the mag 8.1 earthquake near
CTIO.

DECam has a 3 sq-deg field of view, and typically reaches i,z = 23rd
limiting magnitudes for 90 sec exposure times. In 2015-09-18 and
2015-09-17, we covered a total of 6% of the LIGO probability map in 3
hours of observing time. We imaged a total of 93 sq-deg to 23.25
5-sigma point source limiting magnitude in i,z bands.��
Coordinates for both nights are given below.
Analysis is underway.

6 pointings in 2015-09-18
    ra        dec
62.107867  -57.8027
120.622213 -67.14873
129.784212 -68.71983
132.961775 -65.42426
133.801654 -67.3675
77.530833  -66.03508

28 pointings in 2015-09-17
    ra        dec
105.241671 -69.46246
72.711983  -65.40533
99.430667  -69.84
68.298046  -63.8895
95.986417  -68.35239
110.757033 -68.87642
115.898475 -68.09865
109.488283 -70.73343
103.3931   -71.25164
115.164875 -70.00358
120.35765  -69.0844
65.041267  -62.8751
93.434754  -69.99717
65.802783  -60.8461
62.9234    -59.8316
125.044417 -67.99968
129.235458 -66.77258
68.870837  -61.8606
125.215963 -69.94243
72.150367  -62.8751
62.107867  -57.8027
87.38715   -69.92876
83.908596  -71.39367
81.427092  -69.63706
84.793617  -68.22478
82.565254  -66.48404
79.328883  -67.84927
77.530833  -66.03508

[GCN OPS NOTE(20sep15): This Circular was originally published on 19:51 20-Sep-2015 UT.]