GCN Circular 21564
Subject
LIGO/Virgo G298048: AGILE-GRID analysis of the potential counterpart field
Event
Date
2017-08-18T15:22:43Z (8 years ago)
From
Francesco Verrecchia at ASDC, INAF-OAR <verrecchia@asdc.asi.it>
A. Bulgarelli (INAF/IASF-Bo), M. Tavani (INAF/IAPS, and Univ. Roma Tor
Vergata), F. Verrecchia (SSDC and INAF/OAR), M. Cardillo, G. Piano
(INAF/IAPS), M. Pilia (INAF/OA-Cagliari), C. Pittori (SSDC and INAF/OAR),
I. Donnarumma (ASI), F. Longo (Univ. Trieste and INFN Trieste), A. Ursi,
G. Minervini, A. Argan, Y. Evangelista (INAF/IAPS), F. Lucarelli (SSDC and
INAF/OAR), N. Parmiggiani, A. Zoli, V. Fioretti, F. Fuschino (INAF/IASF-Bo),
A. Trois (INAF/OA-Cagliari), M. Marisaldi (INAF/IASF-Bo and Bergen University),
A. Giuliani (INAF/IASF-Mi), report on behalf of the AGILE Team:
As reported in previous GCNs of the AGILE Team (LVC GCN 21525 and 21526)
at the G298048 event time T0 the 90% localization region (LR) of the HLV
skymap was not accessible to AGILE detectors because of a prolonged Earth
occultation of that portion of the sky.
AGILE is currently spinning and is scanning about 80% of the entire sky
every 7 minutes. The G298048 HLV LR was exposed before and after T0 with a
complex pattern that depends on the instrument boresight revolution and Earth
occultation.
In the analysis results reported below, we use the updated G298048 sky map
(LVC GCN 21527) including the optical transient SSS17a (RA = 13:09:48.09
DECL. = -23:22:53.35, Coulter et al. 2017; LVC GCN 21529) which is
the potential optical counterpart (see also Allam et al. LVC GCN 21530,
Yang et al. LVC GCN 21531, Melandri et al. LVC GCN 21532) to G298048.
The closest in time AGILE-GRID detector exposure of the G298048 LR
starts near T0+950 sec. For an integration time ranging from T0+950 to
T0+1100 sec, we obtained the 3-sigma gamma-ray flux upper limit
UL_1 = 5.7e-08 erg cm^2 s^-1 at energies above 100 MeV at the optical
transient location.
Previously, the closest in time passage of the AGILE-GRID instrument over
the LR occurred at times from T0-1950 to T0-1750 sec before T0. For this
exposure we obtained the 3-sigma gamma-ray flux upper limit UL_2 = 3.4e-08
erg cm^2 s^-1 at energies above 100 MeV at the optical transient location.
We also carried out an analysis on longer timescales. For an integration
time during a 10 ksec time window preceding T0, we obtain an AGILE-GRID
gamma-ray flux upper limit of UL_3 = 2.8e-09 erg cm^-2 s^-1
at the optical transient location at energies above 100 MeV.
For an integration time of 10 ksec following T0, we obtain UL_4 = 3.5e-09
erg cm^-2 s^-1 at energies above 100 MeV at the optical transient location.
No significant new sources were found in our analysis. Additional analysis
of AGILE data is ongoing.