{
  "bibcode": "2020GCN.26794....1S",
  "body": "D.Steeghs (1); K.Ulaczyk (1); J.Lyman (1); R.Cutter (1); T.Killestein\n(1); M.Dyer (3); M.Kennedy (10); G.Ramsay (5); D.K.Galloway (2);\nV.Dhillon (3); P.O'Brien (4); D.Pollacco (1); E.Thrane (2);\nS.Poshyachinda (6); S.Mattila (7); L.Nuttall (8); E.Palle (9);\nA.Levan (1); T.Marsh (1); R.West (1); E.Stanway (1); B.Gompertz (1);\nK.Wiersema (1); ; K.Ackley (2); Y.-L.Mong (2); A.Casey (2); M.Brown\n(2); B.Muller (2); J.Mullaney (3); E.Daw (3); S.Littlefair (3);\nJ.Maund (3); L.Makrygianni (3); R.Starling (4); R.Eyles (4); S.Tooke\n(4); S.Aukkaravittayapun (6); U.Sawangwit (6); S.Awiphan (6);\nD.Mkrtichian (6); P.Irawati (6); R.Kotak (7); T.Heikkila (7); E.Rol\n(2)\n\n(1) Warwick University, (2) Monash University, (3) University of\nSheffield, (4) University of Leicester, (5) Armagh Observatory &\nPlanetarium, (6) National Astronomical Research Institute of\nThailand, (7) University of Turku, (8) University of Portsmouth, (9)\nInstituto de Astrofisica de Canarias), (10) Univ. of Manchester.\n\nreport on behalf of the GOTO collaboration:\n\nWe report on optical observations with the Gravitational-wave Optical\nTransient Observer prototype in response to S200115j (GCN #26759).\nTargeted observations started shortly after the preliminary event\nnotification was received. These spanned 43 distinct tile pointings\ncontaining 59.6% of the source location probability (based on the\ninitial BAYESTAR skymap) and were acquired between 04:34 UT Jan 15\n2019 and 06:55 UT Jan 16 2019 (starting 11 minutes after the event\ntime).\n\nEach pointing spans 4.9x3.7 square degrees and consisted of 3x60s\nexposures in our L-band filter (400-700nm passband similar to g+r)\nwith a median 5-sigma photometric depth equivalent to g=19.5 for an\nindividual pointing. Limits are based on a photometric calibration\nagainst PS1 sources. Most pointings were observed multiple times,\ntypically 2-3 times.\n\nImages are processed immediately after acquisition using the\nGOTOphoto pipeline. Difference imaging was performed on the median of\neach triplet of exposures using recent survey observations of the\nsame pointings. Source candidates were initially filtered using a\nclassifier and cross-matched against a variety of catalogs, including\nthe MPC and PS1. Human candidate vetting was performed following data\nacquisition and automated classifier cuts. For a small number of\ntiles no suitable reference frames were available, reducing the\nsearched probability area to 51.7%.\n\nNo new transients were detected that could be credibly associated\nwith S200115j. We did not detect any significant sources at the\nlocation of the reported ZTF candidates (GCN #26767), as expected\ngiven our limiting magnitudes for those exposures.\n\n\nGOTO is operated at the La Palma observing facilities of the\nUniversity of Warwick on behalf of a consortium including the\nUniversity of Warwick, Monash University, Armagh Observatory, the\nUniversity of Leicester, the University of Sheffield, the National\nAstronomical Research Institute of Thailand (NARIT), The University\nof Portsmouth, the University of Turku and the Instituto de\nAstrofisica de Canarias (IAC) (https://goto-observatory.org/)",
  "circularId": 26794,
  "createdOn": 1579220200000,
  "email": "dsteeghs@gmail.com",
  "subject": "LIGO/Virgo S200115j: No notable candidates in GOTO imaging",
  "submitter": "Danny Steeghs at U.of Warwick/GOTO  <dsteeghs@gmail.com>",
  "eventId": "LIGO/Virgo S200115j"
}