TITLE: GCN CIRCULAR NUMBER: 20937 SUBJECT: INTEGRAL pointed follow-up of IceCube-170321A DATE: 17/03/25 18:40:15 GMT FROM: Volodymyr Savchenko at ISDC,U of Geneve 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 keV. 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.