{
  "bibcode": "2018GCN.23379....1C",
  "body": "Authors: Michael W. Coughlin (Caltech), Tom��s Ahumada (UMD), S.\nBradley Cenko (NASA GSFC), Shaon Ghosh (UWM), Virginia Cunningham\n(UMD), Eric C. Bellm (UW), Mansi M. Kasliwal (Caltech) and Leo P.\nSinger (NASA GSFC) on behalf of the ZTF and GROWTH collaborations\n\nWe observed the localization region of the short GRB 180728B (trigger\n554505003) detected by the Gamma-Ray Burst Monitor (GBM) on the Fermi\nsatellite with the Palomar 48-inch telescope equipped with the 47\nsquare degree Zwicky Transient Facility (ZTF) camera. The observations\ntaken during the night of July 29 did not cover the IPN updated\nlocalization of GRB 180628B available the next day.  The IPN region\nwas observed with ZTF beginning at 04:06 UT on 2018 July 30 (30:58\nhours after the trigger time). The observations covered 334 square\ndegrees, corresponding to ~ 76% of the probability enclosed in the\nlocalization region.\n\nThe images were processed through the ZTF reduction and image\nsubtraction pipelines at IPAC to search for potential counterparts. 7\nhigh-significance transient and variable candidates were identified by\nour pipeline in the area observed, all of which had previous\ndetections with ZTF in the days and weeks prior to the GRB trigger\ntime (e.g., supernovae, active galactic nuclei). No viable optical\ncounterparts were thus identified.\n\nThe median 5-sigma upper limit for an isolated point source in our\nimages was r > 18.7 and g > 20. mag for the observations made on July\n30.\n\nZTF is a project led by PI S. R. Kulkarni at Caltech (see ATEL\n#11266), and includes IPAC; WIS, Israel; OKC, Sweden; JSI/UMd, USA;\nUW, USA; DESY, Germany; NRC, Taiwan; UW Milwaukee, USA and LANL USA.\nZTF acknowledges the generous support of the NSF under AST MSIP Grant\nNo 1440341. Alert distribution service provided by DIRAC@UW. Alert\nfiltering is being undertaken by the GROWTH marshal system, supported\nby NSF PIRE grant 1545949.",
  "circularId": 23379,
  "createdOn": 1540410005000,
  "email": "mcoughli@caltech.edu",
  "subject": "GRB 180728B: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 554505003)",
  "submitter": "Michael Coughlin at Caltech/LIGO  <mcoughli@caltech.edu>",
  "eventId": "GRB 180728B"
}