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GCN Circular 20754

LIGO/Virgo G275404: AGILE-GRID detection of a possible gamma-ray transient
2017-02-26T16:26:01Z (7 years ago)
Francesco Verrecchia at ASDC, INAF-OAR <>
M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A. Giuliani
(INAF/IASF-Mi), A. Bulgarelli (INAF/IASF-Bo), F. Verrecchia (ASDC and
INAF/OAR), P. Munar-Adrover, M. Cardillo (INAF/IAPS),  V. Fioretti, A.
Zoli , N. Parmiggiani (INAF/IASF-Bo), M. Pilia (INAF/OA-Cagliari),  C.
Pittori (ASDC and INAF/OAR), I. Donnarumma, G. Piano (INAF/IAPS), F.
Lucarelli (ASDC and INAF/OAR), 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:

Following up on the analysis of AGILE-GRID data in response to the LIGO/Virgo
GW event G275404, we performed an improved search for transient gamma-ray
emission within the G275404 localization region.

The AGILE-GRID had significant exposure of a good fraction of the G275404
localization region before and after the LIGO trigger time
(T0=2017-02-2518:30:21.374 UT).
Additional analysis in the energy range 30 MeV-50 GeV reveals the existence
of a 3.6-sigma gamma-ray transient event during the interval - 20 / + 10 sec
from T0, at the position with centroid coordinates: R.A.= 288.43 deg,
DEC= 10.72 deg (Galactic l = 45.0, b = 0.0), and error radius R = 4 deg
(stat. 68% confidence) + 1 deg (syst.). We name this transient AGL J1914+1043.

Despite its weakness, we consider AGL J1914+1043 an interesting source
candidate for its timing properties and position within the G275404
localization region.

No MCAL trigger event was recorded on board in coincidence with AGL
J1914+1043 which appears to be detected only at energies above 70 MeV.

This measurement was obtained with AGILE observing a large portion of the
sky in spinning mode. Additional analysis of AGILE data is in progress.
Multifrequency observations of the AGL J1914+1043 field are encouraged.
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