{
  "bibcode": "2018GCN.22871....1C",
  "body": "Michael W. Coughlin (Caltech), Leo P. Singer (NASA GSFC), Tom��s Ahumada\n(UMD), S. Bradley Cenko (NASA GSFC), Shaon Ghosh (UWM), Mansi M. Kasliwal\n(Caltech), Eric C. Bellm (UW), V. Zach Golkhou (UW), Ludwig Rauch (DESY),\nRobert Stein (DESY), on behalf of the ZTF and GROWTH collaborations and the\nKPED team\n\nWe observed the localization region of the short GRB 180626C (trigger\n551697835) detected by the Gamma-Ray Burst Monitor (GBM) on the Fermi\nsatellite with the Palomar 48 inch telescope equipped with the 47 square\ndegree Zwicky Transient Facility (ZTF) camera. We obtained a series of r-\nand g-band images covering 275 square degrees beginning at 10:52 UT on 2018\nJune 26 (1:29 hours after the burst trigger time), corresponding to ~ 36%\nof the probability enclosed in the localization region.  Using the IPN\nupdated localization of GRB 180626C available the next day, we observed the\nnew region with ZTF beginning at 05:01 UT on 2018 June 27 (19:43 hours\nafter the trigger time). The observations covered 230 square degrees,\ncorresponding to ~ 87% of the probability enclosed in the localization\nregion.\n\nThe images were processed through the ZTF reduction and image subtraction\npipelines at IPAC to search for potential counterparts. 45\nhigh-significance transient and variable candidates were identified by our\npipeline in the area observed, all of which had previous detections with\nZTF in the days and weeks prior to the GRB trigger time (e.g., supernovae,\nactive galactic nuclei). Out of the 45 transients, only 1 transient was\nwithin the IPN localization region, but the object has previous detections\nat similar magnitudes. No viable optical counterparts were thus identified.\n\nWe would like to highlight one interesting object discovered in the ZTF\nfields on the first night (it does not fall into the IPN localization\nregion) and later followed up with the Kitt Peak EMCCD Demonstrator (KPED)\non the Kitt Peak 84 inch telescope on June 27. Located at RA: 19:48:49.1 ,\nDEC: +46:30:36.1, ZTF18aauebur was first detected by ZTF June 25.30 (1 day\nbefore the trigger); it is a rapidly evolving transient that has gone from\ng = 18.4 to g = 20.5 in 1.92 days.  An underlying source is present at this\nlocation in Pan-STARRS DR1 and GALEX. Given the low Galactic latitude, it\nmay be a stellar flare.\n\nThe median 5 sigma upper limit for an isolated point source in our images\nwas r > 20.9 and g > 20.9 mag for the observations made on June 26 and r >\n21.2 and g > 21.0 mag for the observations made on June 27.\n\nZTF is a project led by PI S. R. Kulkarni at Caltech (see ATEL #11266\n<http://www.astronomerstelegram.org/?read=11266>), and includes IPAC; WIS,\nIsrael; OKC, Sweden; JSI/UMd, USA; UW, USA; DESY, Germany; NRC, Taiwan; UW\nMilwaukee, USA and LANL USA. ZTF acknowledges the generous support of the\nNSF under AST MSIP Grant No 1440341. Alert distribution service provided by\nDIRAC@UW. Alert filtering is being undertaken by the GROWTH marshal system,\nsupported by NSF PIRE grant 1545949.\n\n[GCN OPS NOTE(01jul18): Per author's request, the \"A\"s in the Subject-line\nand in the two places in the first paragraph were changed to \"C\"s.  And the\nTrigger number in the Subject-line was changed to 551697835.]",
  "circularId": 22871,
  "createdOn": 1530330361000,
  "email": "mcoughli@caltech.edu",
  "subject": "GRB 180626C: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 551697835)",
  "submitter": "Michael Coughlin at Caltech/LIGO  <mcoughli@caltech.edu>",
  "eventId": "GRB 180626C"
}