{
  "bibcode": "2019GCN.25199....1K",
  "body": "Mansi M. Kasliwal (Caltech), Leo P. Singer (NASA GSFC), Eric C. Bellm (UW),\nMichael W. Coughlin (Caltech), Daniel A. Perley (LJMU), Jesper Sollerman\n(OKC), Igor Andreoni (Caltech), Erik Kool (OKC), Danny Goldstein (Caltech),\nRahul Biswas (OKC), Richard Walters (Caltech), Varun Bhalerao (IITB), G. C.\nAnupama (IIA), Shreya Anand (Caltech), Tomas Ahmuda (UMD), Brad Cenko (NASA\nGSFC), Sara Webb (Swinburne), Jeff Cooke (Swinburne), Kirsty Taggart\n(LJMU), Sudhanshu Barway (IIAP), Alessandra Corsi (TTU), Mattia Bulla\n(OKC), Albert Kong (Taiwan), Chris Copperwheat (LJMU)\n\nOn behalf of the Zwicky Transient Facility (ZTF) and Global Relay of\nObservatories Watching Transients Happen (GROWTH) collaborations\n\nWe observed the localization region of the gravitational wave trigger\nS190728q (GCN 25187) with the Palomar 48-inch telescope equipped with the\n47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). A new\ntiling was automatically optimally determined and triggered using the\nGROWTH Target of Opportunity marshal (Coughlin et al. 2019a, Kasliwal et\nal. 2019b). We enclosed 64% of the probability and obtained a sequence of\n300s exposures in g-band, r-band and g-band before sunrise.\n\nThe images were processed through the ZTF reduction and image subtraction\npipelines at IPAC to search for potential counterparts (Masci et al. 2019).\nWe applied standard filtering criterion including rejecting stellar sources\n(Tachibana and Miller 2018) and moving objects and applying machine\nlearning algorithms (Mahabal et al. 2019, Duev et al. 2019).\n\nA promising candidate with the first detection after the GW merger time and\na fast intra-night rise in both filters is:\n-------------------------------------------------------------------------------------------------------------------\n ZTF Name     | RA (deg)    | DEC (deg)   | Filter | Mag   |  Magerr |\nFilter | Mag   | Magerr\n--------------------------------------------------------------------------------------------------------------------\nZTF19abjethn  | 326.395431 | 20.690590    | r      | 19.65 |  0.11   | g\n  | 19.82 |  0.16\n--------------------------------------------------------------------------------------------------------------------\n\nWe reported this candidate to TNS and it was given the name AT2019lvs. The\ncandidate is offset from a galaxy with SDSS phot-z estimate of 0.228 ��\n0.0286. We serendipituously observed this field the previous night with ZTF\nand did not detect the candidate.\n\nAdditional analysis and continued follow-up is in progress and encouraged.\n\nZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC,\nUSA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY,\nGermany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan;\nIIT-B, India; IIA, India; LJMU, UK; TTU, USA; and USyd, Australia. ZTF\nacknowledges the generous support of the NSF under AST MSIP Grant No\n1440341. GROWTH acknowledges generous support of the NSF under PIRE Grant\nNo 1545949. Alert distribution service provided by DIRAC@UW (Patterson et\nal. 2019). Alert filtering and follow-up co-ordination is being undertaken\nby the GROWTH marshal system (Kasliwal et al. 2019).",
  "circularId": 25199,
  "createdOn": 1564326402000,
  "email": "mansikasliwal@gmail.com",
  "subject": "LIGO/Virgo S190728q: Optical Candidate from the Zwicky Transient Facility ZTF19abjethn",
  "submitter": "Mansi M. Kasliwal at Caltech/Carnegie  <mansikasliwal@gmail.com>",
  "eventId": "LIGO/Virgo S190728q"
}