{
  "bibcode": "2018GCN.23324....1C",
  "body": "Michael W. Coughlin (Caltech), S. Bradley Cenko (NASA GSFC), Tom��s\nAhumada (UMD), Leo P. Singer (NASA GSFC), Shaon Ghosh (UWM), Igor\nAndreoni (Caltech), Mansi M. Kasliwal (Caltech), Eric C. Bellm (UW),\nV. Zach Golkhou (UW), on behalf of the ZTF and GROWTH collaborations\nand the KPED team\n\nWe observed the localization region of the short GRB 180913A (trigger\n558557292) 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. We obtained a\nseries of 180 second g-, r- and g-band images covering 546 square\ndegrees beginning at 3:06 UT on 2018 September 14 (8:18 hours after\nthe burst trigger time). Accounting for area lost to processing\nfailures due to the overlap of the region with the Galactic plane,\nthis corresponds to analyzing 72% of the probability enclosed.  Using\nthe IPN updated localization of GRB 180913B available the next day, we\nobserved the IPN region with ZTF beginning at 3:08 UT on 2018\nSeptember 15, using 300 second g-, r- and g-band exposures. The\nobservations covered 403 square degrees. Once again accounting for\nprocessing failures, 53% of the enclosed probability was analyzed. A\nthird set of the same epochs was taken beginning at 3:06 UT on 2018\nSeptember 19, using 300 second g-band and 180 second r-band exposures.\n\nThe images were processed through the ZTF reduction and image\nsubtraction pipelines at IPAC to search for potential counterparts.\n296 high-significance transient and variable candidates were\nidentified by our pipeline in the area observed,  most (284) of which\nhad previous detections with ZTF in the days and weeks prior to the\nGRB trigger time (e.g., supernovae, active galactic nuclei). The 12\ntransients discovered the night of September 14 are listed in the\ntable below. These candidates were followed up with the Kitt Peak\nEMCCD Demonstrator (KPED) on the Kitt Peak 84 inch telescope on\nSeptember 16 and with the fl05 Sinistro Camera at Las Cumbres\nObservatory (LCO) node at McDonald Observatory on September 23. .\n\n----------------------------------------------------------------------------------------------------------------------------\n\n       ZTF ID             RA DEC      last non-detection discovery mag\n     KPED mag\n\n----------------------------------------------------------------------------------------------------------------------------\n\n\n                       2018/09/14 2018/09/17\n\n----------------------------------------------------------------------------------------------------------------------------\nZTF18abvzgms     354.4607 47.8892      2018/09/12 g>20.96 g = 21.96\n       g = 19.65\nZTF18abwiios        348.0586 39.4641     2018/09/12 g>20.92 g = 22.04\n         g = 20.24\n\nZTF18abvzfgy        349.0633 43.5331    2018/09/12 g>20.98  g = 20.98 g = 20.36\n\nZTF18abvzjwk       337.6354 39.8374     2018/09/12 g>20.72   g = 21.70 g = 21.80\n\nZTF18abvwkbw     344.1347 37.0509     2018/09/13 r>20.64    r = 21.19\n  r > 23.12\n\nZTF18abvwhkl      346.4340 45.543      2018/09/12 r>20.60   r = 21.44 r = 21.15\n\nZTF18abvucnv       337.8832 39.501      2018/09/12 g>20.85 g = 21.15\n         g = 20.88\n\nZTF18abwiitm        348.8650 39.9529    2018/09/12 g>20.91   g = 21.71 g = 20.9\n\nZTF18abvubdm     344.6185 47.1011     2018/09/12 g>20.86 g = 21.01\n      g = 20.19\n\nZTF18abvzsld            3.988 49.4808 2018/09/13  g>20.99 g = 21.50 g = 21.14\n\nZTF18abwiivr         343.0658 37.3748      2018/09/14 g=21.73 2018/09/12 g>20.89\n\nZTF18abvzmtm     358.8045 48.3605        2018/09/14 g=21.65 2018/09/13 g>21.01\n\n-------------------------------------------------------------------------------------------------------------------------\n\nThe median 5 sigma upper limit for an isolated point source in our\nimages was g > 21.8 and r > 22.2 mag for the observations made on\nSeptember 14 and g > 21.9 and g > 22.1 mag for the observations made\non September 15. For the LCO observations, the median 5 sigma upper\nlimit for an isolated point source in our images was g> 20.2 and\nr>19.9 , no transient had risen to these magnitudes by September 23.\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": 23324,
  "createdOn": 1539272965000,
  "email": "mcoughli@caltech.edu",
  "subject": "GRB180913A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 558557292)",
  "submitter": "Michael Coughlin at Caltech/LIGO  <mcoughli@caltech.edu>",
  "eventId": "GRB 180913A"
}