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GCN Circular 24951

Subject
LIGO/Virgo S190701ah: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
Date
2019-07-01T21:40:13Z (5 years ago)
From
Alexis Coleiro at APC/U. Paris Diderot <coleiro@apc.in2p3.fr>
A. Coleiro (APC, France), F. Onori (IAPS-Roma, Italy)
V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland)
J. Rodi (IAPS-Roma, Italy)
S. Mereghetti (INAF IASF-Milano, Italy)

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

Using INTEGRAL/SPI-ACS realtime data (following [1]) we have performed
a search for a prompt gamma-ray counterpart of S190701ah (GCN 24950).

At the time of the event (2019-07-01 20:33:06 UTC, hereafter T0),
INTEGRAL was operating in nominal mode. The peak of the event
localization probability was at an angle of 75 deg with respect to the
spacecraft pointing axis. This orientation implies strongly suppressed
(18% of optimal) response of ISGRI, strongly suppressed (36% of
optimal) response of IBIS/Veto, and near-optimal (97% 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]) data.

We do not detect any significant counterparts and estimate a 3-sigma
upper limit on the 75-2000 keV fluence of 1.6e-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 ~1.4e-07 (5e-08)
erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range.

For the mean reported distance 1045.0 Mpc this corresponds to the
limit on the total isotropic equivalent energy in 1 s of 2.2e+49 erg
for the short GRB spectrum and for a long GRB spectrum isotropic
equivalent luminosity in 1 s (8 s) of 1.8e+49 erg/s (6.5e+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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