TITLE: GCN CIRCULAR NUMBER: 21437 SUBJECT: LIGO/Virgo G296853: AGILE GRID observations DATE: 17/08/09 16:48:55 GMT FROM: Francesco Verrecchia at ASDC, INAF-OAR F. Verrecchia (SSDC and INAF/OAR), G. Piano (INAF/IAPS), M. Pilia (INAF/OA-Cagliari), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A. Ursi (INAF/IAPS), M. Cardillo, A. Bulgarelli (INAF/IASF-Bo), C. Pittori (SSDC and INAF/OAR), N. Parmiggiani (INAF/IASF-Bo), I. Donnarumma (ASI), A. Giuliani (INAF/IASF-Mi), F. Lucarelli (ASDC and INAF/OAR), G. Minervini (INAF/IAPS), F. Longo (Univ. Trieste and INFN Trieste), F. Fuschino (INAF/IASF-Bo), Y. Evangelista (INAF/IAPS), M. Marisaldi (INAF/IASF-Bo and Bergen University), A. Argan (INAF/IAPS), A. Trois (INAF/OA-Cagliari), V. Fioretti (INAF/IASF-Bo), report on behalf of the AGILE Team: In response to the LIGO/Virgo GW trigger G296853 (GCN #21431), we performed an analysis of the AGILE Gamma-Ray Imaging Detector (GRID) data on different timescales. On LIGO trigger time (T0=2017-08-09 08:28:21.747 UTC) the GRID exposure covered more than the 95% of the LIGO localization region, observed at off-axis angles between 5 and 55 deg. An analysis of the data in the energy range 50 MeV - 10 GeV was performed on timescales from 2 to 100 sec centered at T0. Preliminary values of 3-sigma upper limits (UL) obtained within the accessible G296853 localization region are reported below: from 1.4e-06 to 6.0e-06 erg cm^-2 s^-1 for integration time of 2s from 1.4e-07 to 5.6e-07 erg cm^-2 s^-1 for integration time of 20s from 3.1e-08 to 8.4e-08 erg cm^-2 s^-1 for integration time of 100s These ULs apply to a large fraction of the GRID-exposed LIGO localization region. These measurements were obtained with AGILE observing a large portion of the sky in spinning mode. Additional analysis of AGILE data is in progress.