[vsnet-grb-info 24449] LIGO/Virgo S191222n: upper limits from AGILE-GRID observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  26548
SUBJECT: LIGO/Virgo S191222n: upper limits from AGILE-GRID observations
DATE:    19/12/22 08:17:30 GMT
FROM:    Francesco Longo at U of Trieste,INFN Trieste  <franzlongo1969 at gmail.com>

F. Longo (UniTS and INFN Trieste),  M. Pilia (INAF/OA-Cagliari),
M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata),
M. Cardillo, C. Casentini, G. Piano, A. Ursi (INAF/IAPS),
F. Lucarelli, C. Pittori, F. Verrecchia (SSDC, and INAF/OAR),
A. Bulgarelli, V. Fioretti, N. Parmiggiani (INAF/OAS-Bologna),
report on behalf of the AGILE Team:

In response to the LIGO-Virgo GW event S191222n at T0 = 2019-12-22
03:35:37.119 (UT) a preliminary analysis of the AGILE exposure at T0
shows that the Gamma-Ray Imaging Detector (GRID) exposure covered
the 38% of the 90% c.l. localization region (LR) (19% of the LR was
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 S191222n 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 7.8e-07 to 4e-06 erg cm^-2 s^-1, with exposure of about 38% of the LR
over the time interval ( T0 -2s ; T0 + 2s );
from 3.2e-07 to 1.6e-06 erg cm^-2 s^-1, with exposure of about 38% of
the LR over the time interval ( T0s ; T0 + 10s );
from 3.4e-08 to 3.5e-06 erg cm^-2 s^-1, with exposure of about 42% of
the LR over the time interval ( T0s ; T0 + 100s );

These measurements were obtained with AGILE observing a large portion of
the sky in spinning mode. Additional analysis of AGILE data is in progress.