TITLE: GCN CIRCULAR NUMBER: 24186 SUBJECT: LIGO/Virgo S190425z: AGILE-GRID Observations DATE: 19/04/25 15:41:12 GMT FROM: Giovanni Piano at INAF-IAPS G. Piano, C. Casentini (INAF/IAPS), F. Verrecchia (SSDC, and INAF/OAR), A. Ursi, M.Cardillo (INAF/IAPS), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), F. Lucarelli, C. Pittori (SSDC, and INAF/OAR), A. Bulgarelli, N. Parmiggiani (INAF/OAS-Bologna), M. Pilia (INAF/OA-Cagliari), F. Longo (Univ. Trieste, and INFN Trieste), report on behalf of the AGILE Team: In response to the LIGO-Virgo GW event S190425z at T0 = 2019-04-25 08:18:05 (UT), we performed a preliminary analysis of the AGILE Gamma-Ray Imaging Detector (GRID). We divided the LIGO/Virgo localization region (LR) 90% c.l. into two parts: the first with R.A. in the approximate range between 1 - 8 hr, the second with R.A. in the approximate range between 12 - 20 hr. For the first part of the LR, we analyzed the first interval available with a good coverage, between T0+100s and T0+200s. In this time interval, the GRID exposure covered nearly 60% of the first part of the LR, observed at off-axis angles between 25 deg and 70 deg. An analysis of the data in the energy range 50 MeV - 10 GeV in this integration time was performed and preliminary 3-sigma upper limits (ULs) values within the accessible LIGO/Virgo LR are: from 4.1e-8 erg cm^-2 s^-1 to 4.5e-7 erg cm^-2 s^-1 for an integration time of 100s. In the time interval between T0-200 and T0+300, the GRID exposure covered nearly 100% of the first part of the LR, observed at off-axis angles between 0 deg and 70 deg. An analysis of the data in the energy range 50 MeV - 10 GeV in this integration time was performed and preliminary 3-sigma ULs are: from 1.4e-8 erg cm^-2 s^-1 to 3.2e-8 erg cm^-2 s^-1 for an integration time of 500s. Between T0+700s and T0+800s the GRID exposure covered nearly 15% of the second part of the LR, observed at off-axis angles between 40 deg and 70 deg. An analysis of the data in the energy range 50 MeV - 10 GeV in this integration time was performed and preliminary 3-sigma ULs are: from 4.2e-8 erg cm^-2 s^-1 to 2.3e-7 erg cm^-2 s^-1 for an integration time of 100s. In the time interval between T0+700 and T0+2000, the GRID exposure covered nearly 95% of the second part of the LR, observed at off-axis angles between 40 deg and 70 deg. An analysis of the data in the energy range 50 MeV - 10 GeV in this integration time was performed and preliminary 3-sigma ULs are: from 7.8e-9 erg cm^-2 s^-1 to 4.3e-8 erg cm^-2 s^-1 for an integration time of 1300s. These measurements were obtained with AGILE observing a large portion of the sky in spinning mode.