[vsnet-grb-info 22044] AT LIGO-Virgo S190421ar: AGILE GRID observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  24143
SUBJECT: AT LIGO-Virgo S190421ar: AGILE GRID observations
DATE:    19/04/22 18:30:44 GMT
FROM:    Martina Cardillo at INAF-IAPS  <martina.cardillo at inaf.it>

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

In response to the LIGO-Virgo GW event S190421ar T0 = 2019-04-21 
21:38:56 (UTC; GCN #24141), analysis of AGILE data shows that the 
satellite at T0 was in the South Atlantic Anomaly (SAA). Scientific 
telemetry was inhibited during the time interval (T0 -600 s; T0 + 400 s).

We performed a preliminary analysis of the AGILE Gamma-Ray Imaging 
Detector (GRID) in the first interval available after the SAA, between 
T0 +450s and T0+550s. In this time interval, the GRID exposure covered 
nearly 55% of the LIGO/Virgo localization region (LR), observed at 
off-axis angles between 15 deg and 60 deg.

An analysis of the data in the energy range 50 MeV - 10 GeV in this 
integration time was performed and preliminary 3-sigma upper limits (UL) 
values within the accessible LIGO/Virgo LR are:
from 4.9e-8 erg cm^-2 s^-1 to 3.0e-7 erg cm^-2 s^-1 for integration time 
of 100s.

These measurements were obtained with AGILE observing a large portion of 
the sky in spinning mode.