TITLE: GCN CIRCULAR NUMBER: 20754 SUBJECT: LIGO/Virgo G275404: AGILE-GRID detection of a possible gamma-ray transient DATE: 17/02/26 16:26:01 GMT FROM: Francesco Verrecchia at ASDC, INAF-OAR M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A. Giuliani (INAF/IASF-Mi), A. Bulgarelli (INAF/IASF-Bo), F. Verrecchia (ASDC and INAF/OAR), P. Munar-Adrover, M. Cardillo (INAF/IAPS), V. Fioretti, A. Zoli , N. Parmiggiani (INAF/IASF-Bo), M. Pilia (INAF/OA-Cagliari), C. Pittori (ASDC and INAF/OAR), I. Donnarumma, G. Piano (INAF/IAPS), F. Lucarelli (ASDC and INAF/OAR), F. Longo (Univ. Trieste and INFN Trieste), A. Ursi (INAF/IAPS), F. Fuschino (INAF/IASF-Bo), Y. Evangelista (INAF/IAPS), M. Marisaldi (INAF/IASF-Bo and Bergen University)(INAF/IAPS), A. Argan, G. Minervini (INAF/IAPS), A. Trois (INAF/OA-Cagliari), report on behalf of the AGILE Team: Following up on the analysis of AGILE-GRID data in response to the LIGO/Virgo GW event G275404, we performed an improved search for transient gamma-ray emission within the G275404 localization region. The AGILE-GRID had significant exposure of a good fraction of the G275404 localization region before and after the LIGO trigger time (T0=2017-02-2518:30:21.374 UT). Additional analysis in the energy range 30 MeV-50 GeV reveals the existence of a 3.6-sigma gamma-ray transient event during the interval - 20 / + 10 sec from T0, at the position with centroid coordinates: R.A.= 288.43 deg, DEC= 10.72 deg (Galactic l = 45.0, b = 0.0), and error radius R = 4 deg (stat. 68% confidence) + 1 deg (syst.). We name this transient AGL J1914+1043. Despite its weakness, we consider AGL J1914+1043 an interesting source candidate for its timing properties and position within the G275404 localization region. No MCAL trigger event was recorded on board in coincidence with AGL J1914+1043 which appears to be detected only at energies above 70 MeV. This measurement was obtained with AGILE observing a large portion of the sky in spinning mode. Additional analysis of AGILE data is in progress. Multifrequency observations of the AGL J1914+1043 field are encouraged.