V. Savchenko (ISDC, University of Geneva, CH),
M. Santander (Barnard College, Columbia University, US),
A. Keivani (Dept. of Physics, Penn State University, US),
E. Gotthelf (Columbia University, US),
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)
On 2017-03-21 07:32:20.69 the IceCube detector has observed a
high-energy neutrino likely of astrophysical origin, IceCube-170321A
(GCN 20929). The location of the event is contained in a circle of
1.2 degree radius (90% confidence) centered at RA=98.30 Dec=-15.02..
INTEGRAL has performed a Target-of-Opportunity observation of the
neutrino localization region, starting 31.5 hours after the neutrino
detection from 2017-03-22 15:10:29 UTC to 2017-03-23 04:30:20 UTC,
corresponding to a total on-target time of 45 ks. IBIS was online for
a fraction of this time, 39.5ks.
We have investigated the data collected by INTEGRAL IBIS and JEM-X
without finding any significant new source in the JEM-X data between 3
and 35 keV within the localization area of IceCube-170321A. In the
IBIS/ISGRI 25-80 keV mosaic image, corresponding to the whole
observation period, we identify an excess with a SNR of 3.9. The
probability of this excess happening randomly in the region of
interest is 3%.
We derived an upper limit on the flux of any new source in the 90%
localization region of IceCube-170321A, averaged over the observation,
of 4 mCrab (1.2x10-10 erg/cm2/s) in 3-35 keV, 3.7 mCrab (3.7x10-11
erg/cm2/s) in 25-80 keV , and 7 mCrab (1.0x10-10 erg/cm2/s) in 80-200
We have also searched for new sources in the whole area covered by the
observation with sensitivity not substantially worse than the deepest
target sensitivity: 16 degree diameter for JEM-X (3-35 keV) and 30
degrees for ISGRI (20-200 keV). We did not find any unidentified
source with a SNR larger than 5.
INTEGRAL/SPI-ACS observations at the time of the neutrino detection is
reported in GCN 20928.
We thank the INTEGRAL Science Operations Centre (ESA/ESAC, Madrid,
Spain) and the Mission Operations Centre (ESA/ESOC, Darmstadt,
Germany) for their prompt scheduling of these observations.