TITLE: GCN CIRCULAR NUMBER: 25515 SUBJECT: LIGO/Virgo S190828l: Upper limits from AGILE-GRID observations DATE: 19/08/28 11:42:48 GMT FROM: Francesco Verrecchia at ASDC F. Longo (Univ. Trieste, and INFN Trieste), F. Verrecchia, C. Pittori (SSDC, and INAF/OAR), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), M. Cardillo, C. Casentini, G. Piano, A. Ursi (INAF/IAPS), F. Lucarelli (SSDC, and INAF/OAR), A. Bulgarelli, V. Fioretti, N. Parmiggiani (INAF/OAS-Bologna), M. Pilia (INAF/OA-Cagliari), report on behalf of the AGILE Team: In response to the LIGO-Virgo GW event S190828l at T0 = 2019-08-28 06:55:09.887 UT a preliminary analysis of the AGILE exposure at T0 shows that the Gamma-Ray Imaging Detector (GRID) exposure covered less than 10% of the 90% c.l. localization region (LR; around 40% of 90% c.l. LR is occulted by Earth). We performed an analysis of the GRID data in the energy range 50 MeV - 10 GeV over time intervals before and after T0, where good exposure of the S190828l 90% c.l. LR was available. No candidate gamma-ray transient was detected. The following preliminary GRID values of 3-sigma upper limit (UL) are obtained: from 3e-08 to 2.e-07 erg cm^-2 s^-1, with exposure of about 50% of the LR over the time interval ( T0 - 100s ; T0 + 0s ); from 8e-08 to 7e-08 erg cm^-2 s^-1, with exposure of about 50% of the LR over the time interval ( T0 + 200s ; T0 + 300s ); These measurements were obtained with AGILE observing a large portion of the sky in spinning mode. Additional analysis of AGILE data is in progress.