TITLE: GCN CIRCULAR NUMBER: 21699 SUBJECT: LIGO/Virgo G299232: INTEGRAL search for a prompt gamma-ray counterpart DATE: 17/08/25 17:06:50 GMT FROM: Volodymyr Savchenko at APC,Paris V. Savchenko (ISDC, University of Geneva, CH) on behalf of the INTEGRAL group: S. Mereghetti (IASF-Milano, Italy), C. Ferrigno ((ISDC, University of Geneva, CH), E. Kuulkers (ESTEC/ESA, The Netherlands), A. Bazzano (IAPS-Roma, Italy), E. Bozzo, T. J.-L. Courvoisier (ISDC, University of Geneva, CH) S. Brandt (DTU - Denmark) R. Diehl (MPE-Garching, Germany) L. Hanlon (UCD, Ireland) P. Laurent (APC, Saclay/CEA, France) A. Lutovinov (IKI, Russia) J.P. Roques (IRAP, France) R. Sunyaev (IKI, Russia) P. Ubertini (IAPS-Roma, Italy) We investigated serendipitous INTEGRAL observations carried out at the time of the LIGO/Virgo GW event candidate G299232. The satellite was pointing at RA=262.993 Dec=-27.052, near the lower-probability arc of LIGO/Virgo localization. About 10% of LIGO localization probability was in IBIS and SPI FoV. Depending on the location within LIGO 90% confidence region the best upper limit is set by the anti-coincidence shield of the spectrometer on board of INTEGRAL (SPI/ACS), IBIS/ISGRI, or IBIS/PICsIT. A fraction of the localization of G299232 is not optimal for SPI-ACS observation. The INTEGRAL IBAS automatically inspects both ISGRI Field of View and all-sky SPI-ACS light curve. It did not reveal any significant excess above the background. We investigated the SPI-ACS, IBIS/PICsIT, and IBIS/ISGRI light curves between -500 and +500 s from the trigger time (2017-08-25 13:13:37 UTC) on temporal scales from 0.1 to 100 s, and found no evidence for any significant deviation from the background. We estimate a median 3-sigma upper limits in 90% LIGO localization region of 1.0e-6 erg/cm2 (75-2000 keV) assuming a duration of 8s and Band model parameters alpha=-1, beta=-2.5, and E_ peak = 300 keV. To derive a limit for a typical short burst with 1 s duration, we use a harder cutoff power law spectrum with a photon index of -0.5 and an Epeak = 500 keV. We find a median limiting fluence of 3.6e-7 erg/cm2 (75-2000 keV) at 3 sigma c.l. For the fraction of LIGO/Virgo localization probability within the Field of View of INTEGRAL pointing instruments (IBIS, JEM-X, and SPI), the combination of these instruments allows to set stringent upper limit in a broad energy range from 3 keV to 8 MeV (Savchenko et al 2017 A&A...603A..46S). Further analysis of these data is ongoing.