GCN Circular 20743

M. Pilia (INAF/OA-Cagliari), M. Tavani (INAF/IAPS, and Univ. Roma Tor
Vergata), P. Munar-Adrover, M. Cardillo (INAF/IAPS), F. Verrecchia (ASDC
and INAF/OAR), A. Bulgarelli, V. Fioretti, A. Zoli , N. Parmiggiani
(INAF/IASF-Bo), C. Pittori (ASDC and INAF/OAR), I. Donnarumma, G. Piano
(INAF/IAPS), F.Lucarelli (ASDC and INAF/OAR), A. Giuliani (INAF/IASF-Mi),
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:

In response to the LIGO/Virgo GW trigger G275404 we performed an analysis
of the AGILE Gamma-Ray Imaging Detector (GRID) data on different
timescales. On LIGO trigger time (T0=2017-02-25 18:30:21.374 UT) the GRID
exposure covered about 30% of the LIGO localization region (in the time
interval T0-100s, T0+100s) that was observed with off-axis angles between
10 and 70 deg.

An analysis of the data in the energy range 50 MeV - 10 GeV was performed
on timescales from 2 to 100 sec centered at T0. Preliminary values of
3-sigma upper limits obtained within the accessible G275404 localization
region are reported below:

1.8e-06 erg cm^-2 s^-1 for integration time of 2s,

1.5e-07 erg cm^-2 s^-1 for integration time of 20s,

3.5e-08 erg cm^-2 s^-1 for integration time of 100s.

These ULs apply to a large fraction of the GRID-exposed LIGO localization
region. We are currently analyzing the significance of a gamma-ray source
candidate within that region.
These measurements were obtained with AGILE observing a large portion of
the sky in spinning mode. Additional analysis of AGILE data is in progress.