TITLE:   GCN CIRCULAR
NUMBER:  24623
SUBJECT: LIGO/Virgo S190521g: No counterpart candidates in AGILE-MCAL observations
DATE:    19/05/21 05:33:20 GMT
FROM:    Claudio Casentini at INAF-IAPS  <claudio.casentini@inaf.it>

C.Casentini (INAF/IAPS), F.Verrecchia (SSDC, and INAF/OAR), M. Tavani
(INAF/IAPS, and Univ. Roma Tor Vergata), M.Cardillo, G.Piano, A.Ursi
(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 S190521g at T0 = 2019-05-21 03:02:29
(UT), a preliminary analysis of the AGILE minicalorimeter (MCAL) triggered
data found no event candidates within a time interval covering 100 sec
preceding the LIGO-Virgo T0. Later times were not covered by MCAL exposure
because of SAA interruption, until about + 800 sec from T0.

Three-sigma upper limits (ULs) are obtained for a 1 s integration time at
different celestial positions within the accessible S190521g 90% c.l.
localization region (almost 60% of the given GW contour), from a minimum of
2.08E-06 erg cm^-2 to a maximum of 8.31E-06 erg cm^-2 (assuming as spectral
model a single power law with photon index 1.5). The average off-axis angle
is about 60 degrees.

The AGILE-MCAL detector is a CsI detector with a 4 pi FoV, sensitive in the
energy range 0.4-100 MeV. Additional analysis of AGILE data is in
progress.