{
  "bibcode": "2016GCN.19377....1M",
  "body": "Title: GCN CIRCULAR\nSubject: VERITAS rapid follow-up observations of IceCube event 160427A\nFrom: VERITAS Collaboration\n\nOn April 27th, 2016, the IceCube collaboration reported the detection of a\nhigh-energy neutrino of potential astrophysical origin (GCN #19363). The\nneutrino event (run ID: 127853, event ID: 67093193) was detected at\n05:52:32 UTC and follow-up observatories, VERITAS among them, were notified\nat 05:53:53 through a GCN/AMON notice.\nSee http://gcn.gsfc.nasa.gov/notices_amon/67093193_127853.amon for details.\n\nVERITAS performed follow-up observations of the alert position (RA:\n239.6639��, Dec: 6.8528��, in J2000 coordinates) between 05:55:45 UTC, 193 s\nafter the neutrino detection, and 07:39:36 UTC in normal ���wobble��� mode,\nwhere the pointing direction of the telescope is offset from the source\nposition to allow for simultaneous measurement of the background. These\nobservations resulted in a total exposure of 71 min, of which 60 min were\ntaken in bright moonlight conditions. No gamma-ray source was detected\nwithin the 50% error circle of the neutrino position (1.6�� radius) or\nanywhere else in the VERITAS field of view which has a diameter of 3.5��.\n\nA second revision of the alert was circulated by IceCube on 04/27/16\n23:24:24 UTC with a refined event position given by more advanced\nreconstruction algorithms. The new alert position (RA: 240.5683��, Dec:\n9.3417��, in J2000 coordinates) was outside the field covered by the first\nVERITAS observations. New observations of the revised position were\nperformed on April 28th between 07:41:32 and 09:47:15 UTC under bright\nmoonlight conditions, resulting in a total exposure of 118 min. No\ngamma-ray source was detected within the 0.6��-radius 90% error circle of\nthe new neutrino position or anywhere else in the VERITAS field of view.\n\nDifferential flux upper limits for a gamma-ray point source were calculated\nat the revised neutrino position (RA: 240.5683��, Dec: 9.3417��, in J2000\ncoordinates) and are listed below for four energy bins, as follows:\n\n----------------------------------------------------\nEmin [TeV]  Emax [TeV]  dN/dE UL [cm^-2 s^-1 TeV^-1]\n----------------------------------------------------\n0.2 0.282 5.7e-11\n0.282 0.398 1.5e-11\n0.398 0.562 2.6e-12\n0.562 0.794 3.0e-12\n\nVERITAS (Very Energetic Radiation Imaging Telescope Array System) is a\nvery-high-energy gamma-ray observatory located at the Fred Lawrence Whipple\nObservatory in southern Arizona, USA.",
  "circularId": 19377,
  "createdOn": 1462235956000,
  "email": "muk@astro.columbia.edu",
  "subject": "VERITAS rapid follow-up observations of IceCube event 160427A",
  "submitter": "Reshmi Mukherjee at Columbia U/VERITAS  <muk@astro.columbia.edu>"
}