TITLE:   GCN CIRCULAR
NUMBER:  22018
SUBJECT: INTEGRAL SPI-ACS observation of IceCube-171015A
DATE:    17/10/15 20:34:06 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. J. Rodi (INAF IAPS-Roma, Italy)
S. Mereghetti (INAF IASF-Milano, Italy)
P. Laurent (CEA, Saclay, France)
E. Kuulkers (ESAC/ESA, Madrid, Spain)

Using INTEGRAL SPI-ACS we have performed a search for a prompt
gamma-ray counterpart of the cosmic neutrino candidate IceCube-171015A
(GCN 22016).

At the time of the event (2017-10-15 01:34:30 UTC, hereafter T0),
INTEGRAL was operating in nominal mode. The neutrino localization was
at an angle of 85 deg with respect to the spacecraft pointing axis.
This orientation implies near-optimal response of SPI-ACS, and this
instrument provides best sensitivity to both short and long GRBs.

The background within +/-300 seconds around the event was very stable.
We do not detect any significant counterparts and estimate a 3-sigma
upper limit on the 75-2000 keV fluence of 2.2x10^-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=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
~1.9x10^-7 (6.2x10^-7) erg/cm^2/s at 1 s (8 s) time scale in 75-2000
keV energy range.