[vsnet-grb-info 22539] LIGO/Virgo S190521r: Upper limits from AGILE-GRID observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  24638
SUBJECT: LIGO/Virgo S190521r: Upper limits from AGILE-GRID observations
DATE:    19/05/21 11:52:18 GMT
FROM:    Francesco Verrecchia at ASDC  <francesco.verrecchia at ssdc.asi.it>

F. Verrecchia (SSDC, and INAF-OAR), C. Casentini (INAF/IAPS), M. Tavani
(INAF/IAPS, and Univ. Roma Tor Vergata),  F. Lucarelli, C. Pittori 
(SSDC, and
INAF-OAR), M. Cardillo, G. Piano A. Ursi (INAF/IAPS), A. Bulgarelli, V.
Fioretti, 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 S190521r at T0 = 2019-05-21 
07:43:59.463
UTC (GCN #24632) a preliminary analysis of the AGILE exposure at T0 showed
the S190521g 90% c.l. localization region (LR) was not exposed by the 
Gamma-Ray
Imaging Detector (GRID). The closest exposure in time occurred at T0-15s
covering about 40% of the LR at off-axis angles between 50 and 60 deg.

We performed an analysis of the GRID data in the energy range 50 MeV - 
10 GeV
over three time intervals before and after T0, when good exposure of
the S190521r 90% c.l. LR was available.

The following preliminary GRID 3-sigma upper limit (UL) values are obtained
over a large area of the exposed LR:

(T0-15s; T0-5s ): from 1.3e-06 to 3.0e-06 erg cm^-2 s^-1, with exposure of
about 40% of the LR;

(T0-100s; T0 ): from 3.5e-08 to 4.5e-07 erg cm^-2 s^-1, with exposure of
about 60% of the LR;

(T0+200s; T0+300s): from 5.2e-08 to 6.4e-07 erg cm^-2 s^-1, with exposure of
about 80% of the LR.

An image of the AGILE-GRID 10s exposure near T0 is available at the site
https://tools.ssdc.asi.it/ImgView/Agile/S190521r_T0-15s_d10s_FM_UL-E50offbm14

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