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GCN Circular 25029

Subject
LIGO/Virgo S190707q: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observations
Date
2019-07-08T07:19:29Z (5 years ago)
From
Celia Sanchez-Fernandez at ISOC/ESA <Celia.Sanchez@sciops.esa.int>
Celia Sanchez-Fernandez (ESA/ESAC, Spain), James Rodi (IAPS-Roma, Italy)
V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland)
A. Coleiro (APC, France)
S. Mereghetti (INAF IASF-Milano, Italy)

on behalf of the INTEGRAL multi-messenger collaboration:
https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration

Using combination of INTEGRAL all-sky detectors (following [1]):
SPI/ACS, IBIS/Veto, and IBIS we have performed a search for a prompt
gamma-ray counterpart of S190707q (GCN 25012).

At the time of the event (2019-07-07 09:33:26 UTC, hereafter T0),
INTEGRAL was operating in nominal mode. The peak of the event
localization probability was at an angle of 169 deg with respect to
the spacecraft pointing axis. This orientation implies strongly
suppressed (3.3% of optimal) response of ISGRI, near-optimal (88% of 
optimal)
response of IBIS/Veto, and strongly suppressed (38% of optimal) response
of SPI-ACS.

The background within +/-300 seconds around the event was very stable
(excess variance 1.1).

We have performed a search for any impulsive events in INTEGRAL SPI-ACS
(as described in [2]), IBIS, and IBIS/Veto data.

We do not detect any significant counterparts and estimate a 3-sigma
upper limit on the 75-2000 keV fluence of 2.6e-07 erg/cm^2 (within the
50% probability containement region of the source localization) for a
burst lasting less than 1 s with a characteristic short GRB spectrum
(an exponentially cut off power law with alpha=-0.5 and Ep=600 keV)
occurring at any time in the interval within 300 s around T0. For a
typical long GRB spectrum (Band function with alpha=-1, beta=-2.5, and
Ep=300 keV), the derived peak flux upper limit is ~2.1e-07 (6.4e-08)
erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range.

For the mean reported distance 810.0 Mpc this corresponds to the limit
on the total isotropic equivalent energy in 1 s of 2e+49 erg for the
short GRB spectrum and for a long GRB spectrum isotropic equivalent
luminosity in 1 s (8 s) of 1.7e+49 erg/s (5.1e+48 erg/s)

All results quoted are preliminary.

This circular is an official product of the INTEGRAL Multi-Messenger team.

[1] Savchenko et al. 2017, A&A 603, A46
[2] Savchenko et al. 2012, A&A 541A, 122S



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