{
  "bibcode": "2017GCN.21478....1S",
  "body": "V. Savchenko (ISDC, University of Geneva, CH)\non behalf of the INTEGRAL group:\nS. Mereghetti (IASF-Milano, Italy),\nC. Ferrigno ((ISDC, University of Geneva, CH),\nE. Kuulkers (ESTEC/ESA, The Netherlands),\nA. Bazzano (IAPS-Roma, Italy), E. Bozzo,\nT. J.-L. Courvoisier (ISDC, University of Geneva, CH)\nS. Brandt (DTU - Denmark) R. Diehl (MPE-Garching, Germany)\nL. Hanlon (UCD, Ireland) P. Laurent (APC, Saclay/CEA, France)\nA. Lutovinov (IKI, Russia) J.P. Roques (CESR, France)\nR. Sunyaev (IKI, Russia) P. Ubertini (IAPS-Roma, Italy)\n\nWe investigated serendipitous INTEGRAL observations carried out at the\ntime of the LIGO/Virgo burst candidate G297595.  The satellite was\npointing at RA=240.554 Dec=-55.181, far from the high-probability area\nof LIGO localization. For the full LIGO 90% confidence region the best\nupper limit is set by the anti-coincidence shield of the spectrometer\non board of INTEGRAL (SPI/ACS). The localization of G297595 is close\nto optimal for SPI-ACS observation.\n\nThe INTEGRAL Burst Alert System (IBAS) did not identify any unusual\ntransients in coincidence with the LIGO/Virgo trigger. The IBAS\ninspects both ISGRI Field of View and all-sky SPI-ACS light curve.\n\nWe investigated the SPI-ACS, IBIS/Veto, and IBIS/ISGRI light curves\nbetween -500 and +500 s from the trigger time (2017-08-14 10:30:43\nUTC) on temporal scales from 0.1 to 100 s, and found no evidence for\nany significant deviation from the background.  We estimate maximal \n3-sigma upper\nlimits of 6.6e-7 erg/cm2 (75-2000 keV) for 8s duration assuming Band\nmodel parameters alpha=-1, beta=-2.5, and E_ peak = 300 keV.  To\nderive a limit for a typical short burst with 1 s duration, we use a\nharder cutoff power law spectrum with a photon index of -0.5 and an\nEpeak = 500 keV. We find a limiting fluence of 2.1e-7 erg/cm2 (75-2000\nkeV) at 3 sigma c.l. Due to high particle background at the current\nphase of the Solar Cycle, these upper limits are somewhat higher than\nthose that can be achieved by SPI-ACS in more favorable conditions.\n\nWe do not confirm the report by Pozanenko et al. 2017, GCN 21476. The\nfluctuation they report has an S/N marginally exceeding 3 sigma in an\noptimized time bin used by the authors. In our systematic search, based\non predefined detection thresholds and time bins, this event is not\ndetected with a sufficiently high significance to justify a report. We\nestimate post-trial significance of a long-timescale fluctuation\nshortly following G297595 at 1.9 sigma.\n\nINTEGRAL is scheduled to perform pointed follow-up observations of the\nG297595 localization region.",
  "circularId": 21478,
  "createdOn": 1502727199000,
  "email": "savchenk@apc.in2p3.fr",
  "subject": "LIGO/Virgo G297595: INTEGRAL search for a prompt gamma-ray counterpart",
  "submitter": "Volodymyr Savchenko at APC,Paris  <savchenk@apc.in2p3.fr>",
  "eventId": "LIGO/Virgo G297595"
}