{
"subject": "LIGO/Virgo S190814bv: No counterpart candidates in INTEGRAL SPI-ACS prompt observation",
"bibcode": "2019GCN.25323....1M",
"createdOn": 1565821785000,
"circularId": 25323,
"submitter": "Sandro Mereghetti at IASF-Milano/INAF ",
"email": "sandro.mereghetti@inaf.it",
"body": "Sergey Molkov (IKI, Moscow, Russia), Sandro Mereghetti (INAF IASF-Milano,\nItaly), V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland),\nJ. Rodi (IAPS-Roma, Italy), A. Coleiro (APC, France)\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 a\nsearch for a prompt gamma-ray counterpart of S190814bv.\n\nAt the time of the event (2019-08-14 21:10:39 UTC, hereafter T0), INTEGRAL\nwas operating in nominal mode. The peak of the event\nlocalization probability was at an angle of 117 deg with respect to\nthe spacecraft pointing axis. This orientation implies strongly suppressed\n(3.6% of optimal) response of ISGRI, somewhat suppressed (41% of optimal)\nresponse of IBIS/Veto, and somewhat suppressed (5 1%\nof optimal) response of SPI-ACS.\n\nThe background within +/-300 seconds around the event was very stable\n(excess variance 1.2).\n\nWe have performed a search for any impulsive events in INTEGRAL SPI- ACS\n(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 3.1e-07 erg/cm^2 (within the\n50% probability containement 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 ~2.6e-07 (9.1e-08)\nerg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range.\n\nFor the mean reported distance 236.0 Mpc this corresponds to the limit\non the total isotropic equivalent energy in 1 s of 2.1e+48 erg for the\nshort GRB spectrum and for a long GRB spectrum isotropic equivalent\nluminosity in 1 s (8 s) of 1.7e+48 erg/s (6.1e+47 erg/s)\n\nOverall, in the search region we identify 1 possibly associated\nexcesses:\n\nscale | T | S/N | luminosity ( x 1e49 erg/s) | FAP\n3.1 | 40.9 | 4 | 0.183 +/- 0.0432 +/- 0.0621 | 0.0413\n\n5 likely background excesses:\n\nscale | T | S/N | luminosity ( x 1e49 erg/s) | FAP\n0.45 | -10.7 | 3.5 | 0.398 +/- 0.114 +/- 0.135 | 0.163\n2.5 | 63.9 | 3.1 | 0.155 +/- 0.0481 +/- 0.0525 | 0.443\n1.25 | -34.1 | 3.1 | 0.221 +/- 0.0681 +/- 0.0749 | 0.504\n0.3 | -42 | 3.8 | 0.523 +/- 0.14 +/- 0.178 | 0.591\n0.25 | -53.4 | 4.1 | 0.616 +/- 0.153 +/- 0.209 | 0.616\n\nNote that FAP estimates (especially at timescales above 2s) may be\nfurther affected possibly enhanced non-stationary local backgro und\nnoise. This list excludes any excesses for which FAP is close to unity\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 [2] Savchenko et al. 2012, A&A\n541A, 122S\n\n\n--"
}