GCN Circular 25515

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.