{
"subject": "LIGO/Virgo S191110af: No counterpart candidates in INTEGRAL SPI-ACS, prompt observation",
"bibcode": "2019GCN.26225....1M",
"createdOn": 1573448374000,
"circularId": 26225,
"submitter": "Sergey Molkov at Space Research Inst., Moscow ",
"email": "molkov@iki.rssi.ru",
"body": "Sergey Molkov (IKI, Russia), Maeve Doyle (UCD, Ireland),\nV. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland)\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\nUsing INTEGRAL/SPI-ACS realtime data (following [1]) we have performed\na search for a prompt gamma-ray counterpart of S191110af (GCN 26222).\n\nAt the time of the event (2019-11-10 23:06:44 UTC, hereafter T0),\nINTEGRAL was operating in nominal mode. The peak of the event\nlocalization probability was at an angle of 105 deg with respect to\nthe spacecraft pointing axis. This orientation implies strongly\nsuppressed (6.1% of optimal) response of ISGRI, strongly suppressed\n(22% of optimal) response of IBIS/Veto, and somewhat suppressed (59%\nof optimal) respo nse of SPI-ACS.\n\nThe background within +/-300 seconds around the event was very stable\n(excess variance 1.1).\n\nWe have performed a search for any impulsive events in INTEGRAL\nSPI-ACS (as described in [2]) data.\n\nWe do not detect any significant counterparts and estimate a 3-sigma\nupper limit on the 75-2000 keV fluence of 2.8e-07 erg/cm^2 (within the\n50% probability containment region of the source localization) for a\nburst lasting less than 1 s with a characteristic short GRB spectrum\n(an exponentially cut off power law with alpha=-0.5 and Ep=600 keV)\noccurring at any time in the interval within 300 s around T0. For a\ntypical long GRB spectrum (Band function with alpha=-1, beta=-2.5, and\nEp=300 keV), the derived peak flux upper limit is ~2.4e-07 (8e-08)\nerg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range.\n\nWe report for completeness and in order of FAP, all excesses\nidentified in the search region. We find: 1 possibly associated\nexcess:\n\nscale | T | S/N | flux ( x 1e-06 erg/cm2/s) | FAP\n0.1 | 0.877 | 3.6 | 1.14 +/- 0.312 +/- 0.357 | 0.0497\n\n3 likely background excesses:\n\nscale | T | S/N | flux ( x 1e-06 erg/cm2/s) | FAP\n0.2 | -31 | 3.7 | 0.832 +/- 0.22 +/- 0.261 | 0.735\n0.95 | 185 | 3.8 | 0.385 +/- 0.1 +/- 0.121 | 0.853\n0.65 | 63.2 | 3.4 | 0.413 +/- 0.121 +/- 0.13 | 0.953\n\nNote that FAP estimates (especially at timescales above 2s) may be\npossibly further affected by enhanced non-stationary local background\nnoise. This list excludes any excesses for which FAP is close to\nunity.\n\n\nAll results quoted are preliminary.\n\nThis circular is an official product of the INTEGRAL Multi-Messenger\nteam.\n\n[1] Savchenko et al. 2017, A&A 603, A46\n[2] Savchenko et al. 2012, A&A 541A, 122S\n\n[GCN OPS NOTE(12nov19): Per author's request, the \"unknown\" in the Subject-line\nwas replavced with \"S191110af\".]"
}