[vsnet-grb-info 22147] LIGO/Virgo S190426c: AGILE-GRID Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  24246
SUBJECT: LIGO/Virgo S190426c: AGILE-GRID Observations
DATE:    19/04/26 20:04:13 GMT
FROM:    Giovanni Piano at INAF-IAPS  <giovanni.piano at inaf.it>

G. Piano, M. Cardillo (INAF/IAPS), M. Tavani (INAF/IAPS, and Univ. Roma Tor
Vergata), F. Verrecchia (SSDC, and INAF/OAR), A. Ursi, C. Casentini
(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 S190426c at T0 = 2019-04-26
15:21:55.337 (UT), we performed a preliminary analysis of the AGILE
Gamma-Ray Imaging Detector (GRID) at different timescales in the energy
range 50 MeV - 10 GeV.

At T0 the accessible LIGO/Virgo 90% c.l. localization region (LR), which
includes the Celestial North Pole, was observed at off-axis angles between
10 and 70 deg. Preliminary values of 3-sigma upper limits (UL) obtained at
LIGO/Virgo trigger time (T0) are:

(1) from 5.5e-7 to 3.2e-6 erg cm^-2 s^-1 for an integration time of 5s
starting from T0, with the GRID exposure covered nearly 75% of this part of
the LR.

(2) from 2.8e-7 to 1.6e-6  erg cm^-2 s^-1 for an integration time of 10s
starting from T0, with the GRID exposure covered nearly 80% of this part of
the LR.

(3) from 3.9e-8 to 1.6e-7  erg cm^-2 s^-1 for an integration time of 100s
starting from T0, with the GRID exposure covered 100% of this part of the
LR.

The other part of the LR (R.A. in the approximate range between 10 - 16 hr)
was partly occulted by the Earth at T0, and is currently in the region not
accessible by the GRID because of solar panel constraints.

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