{
  "bibcode": "2017GCN.21263....1G",
  "body": "Adam Goldstein (USRA), Rachel Hamburg (UAH), and Colleen Wilson-Hodge\n(NASA/MSFC) report on behalf of the GBM-LIGO Group:\nLindy Blackburn (CfA), Michael S. Briggs (UAH), Jacob Broida (Carleton\nCollege), Eric Burns (UAH), Jordan Camp (NASA/GSFC), Tito Dal Canton\n(NASA/GSFC), Nelson Christensen (Carleton College), Valerie Connaughton\n(USRA), C. Michelle Hui (NASA/MSFC), Pete Jenke (UAH), Dan Kocevski\n(NASA/MSFC), Nicolas Leroy (LAL), Tyson Littenberg (NASA/MSFC), Julie\nMcEnery (NASA/GSFC), Rob Preece (UAH), Judith Racusin (NASA/GSFC), Peter\nShawhan (UMD), Karelle Siellez (GA Tech), Leo Singer (NASA/GSFC), John\nVeitch (Birmingham), Peter Veres (UAH)\n\nFermi GBM observed 89% of the Bayestar sky map at the time of the LIGO\ntrigger, and we set the following flux upper limits for the entire visible\nsky map (excluded region is a circle with radius of 68 degrees centered on\nRA, Dec = 197.9, 19.5).\n\nUsing a hard Band function with (Epeak, alpha, beta) = (500 keV, -0.5,\n-2.5), we set a 3 sigma, 1-second-averaged flux upper limit for any\ntransient within 30 s of the LIGO trigger time in the 10-1000 keV band\nranging from 4.6e-7 to 9.2e-7 erg/s-cm^2.  Using an exponentially cut-off\npower law parametrized with (Epeak, index) = (566 keV, -0.42), which\nrepresents the average GBM-triggered short GRB, the upper limit ranges from\n5.1e-7 to 9.8e-7 erg/s-cm^2.\n\nUsing the Earth Occultation technique [1] to estimate the amount of\npersistent emission during a 48-hour period centered on the LIGO trigger\ntime, we place the following range of 3-sigma day-averaged flux upper\nlimits based on observed sources over the entire LIGO sky map:\n\nEnergy       min  max  median\n--------------------------------\n 12- 27 keV: 0.07 0.50 0.09 Crab\n 27- 50 keV: 0.12 0.71 0.16 Crab\n 50-100 keV: 0.18 0.97 0.23 Crab\n100-300 keV: 0.33 1.88 0.41 Crab\n300-500 keV: 2.25 14.9 2.84 Crab\n\nThese limits are based on the minimum requirement that each source in the\nEarth Occultation catalog was Earth-occulted at least 6 times in each of\nthe 24 hour periods preceding and following the LIGO trigger and that the\noccultations were well separated from nearby bright sources.\n\nThe location of the Fermi/LAT candidate (Omodei et al., LVC GCN #21227) was\nbehind the Earth at the time of the LIGO trigger. The location came out\nfrom behind the Earth at ~85 s after the LIGO trigger and was visible until\nFermi entered the South Atlantic Anomaly (SAA) ~1 hour later and was then\nbehind the Earth again after Fermi exited the SAA. During this one hour\nwindow, the targeted search ([2], [3]) found three long and spectrally soft\ncandidates (False Alarm Rates of 1 per 2.2 hours, 1 per 1.1 hours, and 1\nper 0.7 hours), all of which localize to the Galactic plane and far from\nthe LAT candidate location.  At ~48 minutes into this one hour window\n(518583038.924 MET / 2017-06-08 02:50:33.924 UTC) another, spectrally\nharder, candidate was found with a duration of ~0.5 s with a False Alarm\nRate of ~1 per 1.5 hours. An initial localization of this candidate\nindicates that the LAT candidate location is within the 2-sigma\nstatistical-only confidence region.  Follow-up analysis and classification\nof this candidate is inconclusive at this time, as is any potential\nassociation with the LAT candidate.  Absent of any GBM counterpart to the\nLAT candidate, we set a 3-sigma, 1-second-averaged flux upper limit that\nranges from 4.7e-7 to 5.6e-7 erg/s-cm^2 during this time window.\n\n[1] C. Wilson-Hodge et al. 2012, ApJS, 201, 33\n[2] L. Blackburn et al. 2015, ApjS 217, 8\n[3] A. Goldstein et al. arXiv:1612.02395",
  "circularId": 21263,
  "createdOn": 1498169043000,
  "email": "adam.michael.goldstein@gmail.com",
  "subject": "LIGO/Virgo G288732: Fermi GBM Upper Limits for the LIGO Trigger and LAT Candidate",
  "submitter": "Adam Goldstein at Fermi/GBM  <adam.michael.goldstein@gmail.com>",
  "eventId": "LIGO/Virgo G288732"
}