TITLE: GCN CIRCULAR
NUMBER: 24589
SUBJECT: LIGO/Virgo S190517h: INTEGRAL prompt observation
DATE: 19/05/18 19:46:13 GMT
FROM: Carlo Ferrigno at IAAT/ISDC
Maeve Doyle, Bozzo Enrico
V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland)
J. Rodi (IAPS-Roma, Italy)
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
At the time of the LIGO/Virgo event S190517h (2019-05-17 05:51:01 UTC,
hereafter T0),
INTEGRAL was operating in nominal mode. The peak of the event
localization probability was at an angle of 90 deg with respect to the
spacecraft pointing axis. This orientation implies a strongly suppressed
(8.7% of optimal) response of ISGRI, strongly suppressed (19% of
optimal) response of IBIS/Veto, and somewhat suppressed (61% of
optimal) response of SPI-ACS.
The background within +/-300 seconds around the event was rather
unstable (excess variance 1.9).
We have performed a search for any impulsive events in INTEGRAL SPI-
ACS (as described in Savchenko et al. 2012, A&A 541A, 122S), 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 2.7e-07 erg/cm^2 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 ~2.3e-07 (1.1e-08)
erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range