TITLE: GCN CIRCULAR NUMBER: 25506 SUBJECT: LIGO/Virgo S190828j: Upper limits from AGILE-GRID observations DATE: 19/08/28 09:07:17 GMT FROM: Francesco Verrecchia at ASDC F. Longo (Univ. Trieste, and INFN Trieste), C. Pittori, F. Verrecchia (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 S190828j at T0 = 2019-08-28 06:34:05.756 UT a preliminary analysis of the AGILE exposure at T0 shows that the Gamma-Ray Imaging Detector (GRID) exposure covered more than 15% of the 90% c.l. localization region (LR) (32% of 90% c.l. localization region (LR) is occulted by Earth). We performed an analysis of the GRID data in the energy range 50 MeV - 10 GeV on T0, where good exposure of the S190828j 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 7.9e-07 to 9.74e-06 erg cm^-2 s^-1, with exposure of about 36% of the LR over the time interval ( T0 -2s ; T0 + 2s ); from 6.5e-07 to 6.1e-06 erg cm^-2 s^-1, with exposure of about 34% of the LR over the time interval ( T0s ; T0 + 5s ); from 3.39e-07 to 6e-06 erg cm^-2 s^-1, with exposure of about 34% of the LR over the time interval ( T0s ; T0 + 10s ); from 1.3e-07 to 5.91e-06 erg cm^-2 s^-1, with exposure of about 36% of the LR over the time interval ( T0s ; T0 + 100s ); A map in Galactic coordinates showing the AGILE FoV at T0 is available at the site: https://tools.ssdc.asi.it/ImgView/Agile/aitoff_MULTImap2019-08-28-4s_mod19 These measurements were obtained with AGILE observing a large portion of the sky in spinning mode. Additional analysis of AGILE data is in progress.