TITLE:   GCN CIRCULAR
NUMBER:  21917
SUBJECT: INTEGRAL SPI-ACS observation of AMON IceCube-170922A
DATE:    17/09/23 09:31:27 GMT
FROM:    Volodymyr Savchenko at ISDC,U of Geneve  <savchenk@in2p3.fr>

V. Savchenko, C. Ferrigno (ISDC, University of Geneva, CH),
P. Ubertini, A. Bazzano, L. Natalucci (INAF IAPS-Roma, Italy),
S. Mereghetti (INAF IASF-Milano, Italy),
P. Laurent (CEA, Saclay, France),
E. Kuulkers (ESTEC/ESA, The Netherlands)

We have exploited INTEGRAL data to search for a prompt gamma-ray
counterpart of the cosmic neutrino candidate AMON IceCube
IceCube-170922A (GCN 21916).

At the time of the event (2017-09-22 20:54:30.4 UTC, hereafter T0),
INTEGRAL was operating in nominal mode. The neutrino localization was
at an angle of 111 deg with respect to the spacecraft pointing axis.
For this orientation the best sensitivity is achieved by SPI-ACS or
IBIS/Veto, depending on the GRB spectrum and duration. The orientation
was not optimal for INTEGRAL observation.

We do not detect any significant counterparts and estimate a 3-sigma
upper limit on the 75-2000 keV fluence of 2.8x10^-7 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=500 keV)
occurring at any time in the interval +-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
7.8x10^-7 erg/cm^2/s 8 s time scale in 75-2000 keV energy range.