{
  "bibcode": "2019GCN.24178....1S",
  "body": "V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland)\nA. Martin-Carillo (UCD, Dublin)\nJ. Rodi (IAPS-Roma, Italy)\nA. Coleiro (APC, France)\nS. Mereghetti (INAF IASF-Milano, Italy)\n\non behalf of the INTEGRAL multi-messenger collaboration:\nhttps://www.astro.unige.ch/cdci/integral-multimessenger-collaboration\n\nWe detect only one possible low-S/N excess after correcting\nfor the local background variance at 2019-04-25T08:18:05\n(T0)+6s, as reported in Martin-Carillo 2019 (GCN 24169).\nIts fluence strongly depends on the true source location,\nsince large 90% localization region provided by LIGO/Virgo\nincludes sky directions in which INTEGRAL detectors able to\ndetect impulsive signal from all-sky (SPI-ACS and IBIS)\nfeatured both low and high sensitivity.\n\nFor the excess at T0+6s, we estimate a possible 75-2000 keV\nfluence range due to uncertainty of the location\nfrom 2.0e-10 to 2e-9 erg/cm2 (in addition to systematic\nuncertainty of response of 20% and statistical uncertainty of 30%),\nassuming the duration of 1s and a characteristic short GRB spectrum\n(an exponentially cut off power law with alpha=-0.5 and Ep=600 keV).\n\nThe sensitivity map is provided:\n\nhttps://www.astro.unige.ch/cdci/content/int-combined-sensitivity-map-lvc-s190425z\n\nWe stress that the FAP of association of this excess to S190425z\nis below 3 sigma. Further estimate of the FAP, taking into account detail\nnoise estimates during the days around the event, will be\nprovided in the future publications.\n\nINTEGRAL is unable to provide an accurate localization of\nthe above mentioned low-S/N excess.\nThe best localization constraint we are currently able to\nprovide excludes the FoV of INTEGRAL/IBIS at the time of the event\n(18:24:43.61, +29:45:25.9, 15 deg radius).\nAn event comparable to the excess at T0+6s occurring in the FoV\nwould have been detected by INTEGRAL/IBAS in realtime.\nFurthermore, a location close to the FoV (within ~30 deg\nfrom the center of the pointing) is discouraged by the lack\nof INTEGRAL IBIS/PICsIT detection.\n\nThe south-west arc of the LIGO/Virgo localization of S190425z\nis slightly unfavorable for the origin of the low-S/N excess,\nif it is associated with the GW signal due to the absence\nof any signal in IBIS/Veto shield.\n\nFurther analysis will be reported in the following circulars.\n\nINTEGRAL has initiated a target of opportunity observation\nof S190425z centered near peak of the LIGO/Virgo localization.\nThe results of these observations will be reported in\nupcoming publications.",
  "circularId": 24178,
  "createdOn": 1556197571000,
  "email": "savchenk@in2p3.fr",
  "subject": "LIGO/Virgo S190425z: further analysis of INTEGRAL data",
  "submitter": "Volodymyr Savchenko at ISDC,U of Geneve  <savchenk@in2p3.fr>",
  "eventId": "LIGO/Virgo S190425z"
}