{
  "bibcode": "2019GCN.24224....1S",
  "body": "D.Steeghs(1), Lyman, J. (1), M.Dyer(3), D.Galloway(2), V.Dhillon(3),\nP.O'Brien(4), G.Ramsay(5), D.Pollacco(1), E.Thrane(2),\nS.Poshyachinda(6), E.Palle(7), K.Ulaczyk(1), R.Cutter(1),\nA.Levan(1), T. Marsh(1), R.West(1), K.Wiersema(1), B.Gompertz(1),\nE.Stanway(1), K.Ackley(2), A.Obradovic(2), Y-L.Mong(2), A.Casey(2),\nM.Brown(2), E.Rol(2), J.Mullaney(3), S.Littlefair(3),\nL.Makrygianni(3), E.Daw(3), J.Maund(3), R.Starling(4), R.Eyles(4),\nU.Sawangwit(6), D.Mkrtichian(6), S.Awiphan(6),S.Aukkaravittayapun(6),\nP.Irawati(6), M.Kennedy(8), R.Breton(8), D.Mata-Sanchez(8),\nT.Heikkila(9), R.Kotak(9)\n(1) Warwick University; (2) Monash University; (3) Univ. of Sheffield;\n(4) University of Leicester; (5) Armagh Observatory;\n(6) National Astronomical Research Institute of Thailand;\n(7) Instituto de Astrofisica de Canarias; (8) Univ. of Manchester;\n(9) University of Turku\n\nreport on behalf of the GOTO collaboration:\n\nWe report on optical observations with the Gravitational-wave Optical\nTransient Observer in response to the BNS event S190425z (GCN #24168).\n\nTargeted observations across 136 pointings containing 29.6% of the\nsource location probability across 2,134 sqr. degrees (based on the\ninitial BAYESTAR skymap) were performed between 20:38 UT Apr 25 and\n05:33 UT Apr 26 2019.\n\nEach pointing spans 4.9x3.7 square degrees and consisted of 3x60s\nexposures in our L-band filter (400-700nm passband) with typical\n5-sigma photometric depth of g=20.1, based on a photometric\ncalibration against PS1 sources. A coverage map is available at\nhttp://goto-observatory.warwick.ac.uk/S190425z.html\n\nImages are processed immediately after acquisition using the GOTOphoto\npipeline. Difference imaging was performed on the median of each\ntriplet of exposures using recent survey observations of the same\npointings. 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 during data\nacquisition and processing in case of notable detections.\n\nWe recover a number of known/already reported transients and variable\nobjects, but no new candidates were detected that could be credibly\nassociated with S190425z.\n\nOur coverage includes some of the PS1 candidates (Smith et al. GCN\n#24210), but we did not cover the position of AT2019ebq/PS19qp, which\nremains an object of interest (Jonker et al. GCN #24221 ; Coughlin et\nal. GCN #24223).\n\nWe also reviewed the locations of the marginal ATLAS candidates\nreported in McBrien et al. (GCN #24197), but detect no sources at\nthese locations, in line with Perley et al. (GCN #24202). The 5-sigma\nlimits are provided below.\n\nName       | IAU Name   | Obs. MJD | Image lim mag (L band 5sig)\nATLAS19hxm |  AT2019dzv | 58598.96 | 20.08\nATLAS19hyx |  AT2019ebl | 58599.03 | 20.63\nATLAS19hyo |  AT2019eao | 58598.93 | 20.50\nATLAS19hwn |  AT2019ebm | 58598.89 | 20.65\nATLAS19hwh |  AT2019ebn | 58598.96 | 20.67\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) and the Instituto\nde Astrofisica de Canarias (IAC) (https://goto-observatory.org/)",
  "circularId": 24224,
  "createdOn": 1556290872000,
  "email": "dsteeghs@gmail.com",
  "subject": "LIGO/Virgo S190425z: GOTO observations",
  "submitter": "Danny Steeghs at U.of Warwick/GOTO  <dsteeghs@gmail.com>",
  "eventId": "LIGO/Virgo S190425z"
}