TITLE: GCN CIRCULAR NUMBER: 21883 SUBJECT: LIGO/Virgo G298048: AST3-2 observations of SSS17a/DLT17ck from Antarctica DATE: 17/09/15 03:45:21 GMT FROM: Igor Andreoni at Swinburne U of Tech Lei Hu (Purple Mountain Observatory), Lifan Wang (Texas A&M University/Purple Mountain Observatory), Tianrui Sun (Purple Mountain Observatory), Ma Bin (National Astronomical Observatory of China), Xiaofeng Wang (Tsinghua University), Xuefeng Wu (Purple Mountain Observatory), and the AST3 team and Jeff Cooke (Swinburne/OzGrav), Igor Andreoni (Swinburne/OzGrav/AAO) on behalf of OzGrav We report observations of the GW counterpart SSS17a/DLT17ck (e.g., Coulter et al., LVC GCN 21529; Allam et al., LVC GCN 21530; Yang et al., LVC GCN 21531) with the second of Antarctica Schmidt Telescopes (AST3-2). AST3-2 is a 50cm optical telescope located at Kunlun Station at Dome A in the Antarctic. Observations were carried out from August 18 through August 28 in g-band filter. Data transfer from Antarctica has recently completed. A source with g-band magnitude 18.15 +/-0.1 was detected on 2017-08-18T14:42.6796 (mean value) at the position of SSS17a/DLT17ck. Note the signal was identified from a coadded image and the observational information about the component images are as follows. Image-ID UT datetime of start of observation Exposure time 0818-48 '2017-08-18T13:58:11.6138' 300.00 0818-49 '2017-08-18T14:03:14.8497' 300.00 0818-50 '2017-08-18T14:09:07.4807' 300.00 0818-51 '2017-08-18T14:14:10.7166' 300.00 0818-52 '2017-08-18T14:28:36.9730' 300.00 All observation from AST3-2 are reported below. All time mentioned is UT time of start of exposure: August 18 The observation is not regular, so we list them in details Group1: observation started from [ID 48]2017-08-18T13:58:11.6138 to [ID 51]2017-08-18T14:14:10.7166 Total 4 images with constant exposure time 300s and regular cadence about 54s Group2: observation started from [ID 52]2017-08-18T14:28:36.9730 to [ID 72]2017-08-18T17:57:39.5806 Total 21 images with constant exposure time 300s and regular cadence about 54s August 20 observation started from [ID 15]2017-08-20T12:51:40.934 to [ID 74]2017-08-20T18:43:29.7538 Total 60 images with constant exposure time 300s and regular cadence about 54s August 21 observation started from [ID 6]2017-08-21T13:10:22.4063 to [ID 55]2017-08-21T17:58:16.8969 Total 50 images with constant exposure time 300s and regular cadence about 54s August 23 observation started from [ID 692]2017-08-23T13:13:02.8477 to [ID 722]2017-08-23T16:10:14.0793 Total 31 images with constant exposure time 300s and regular cadence about 54s August 24 observation started from [ID 871]2017-08-24T15:52:00.3374 to [ID 917]2017-08-24T20:36:43.9922 Total 47 images with constant exposure time 300s and regular cadence about 54s August 25 observation started from [ID 1153]2017-08-25T14:07:25.7058 to [ID 1168]2017-08-25T15:36:08.5704 Total 16 images with constant exposure time 300s and regular cadence about 54s August 27 observation started from [ID 1204]2017-08-27T13:50:45.9777 to [ID 1223]2017-08-27T15:43:31.4251 Total 20 images with constant exposure time 300s and regular cadence about 54s August 28 observation started from [ID 731]2017-08-28T15:12:09.9744 to [ID 738]2017-08-28T15:52:53.1212 Total 8 images with constant exposure time 300s and regular cadence about 54s Processing of the AST3-2 images is in progress.