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AGILE follow-up of the neutrino ICECUBE-160731 event

ATel #9295; F. Lucarelli, C. Pittori, F. Verrecchia (ASDC and INAF/OAR), G. Piano, P. Munar-Adrover (INAF/IAPS), A. Bulgarelli, V. Fioretti, A. Zoli (INAF/IASF-Bo), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), I. Donnarumma (INAF/IAPS), S. Vercellone (INAF/IASF-Pa), G. Minervini (CIFS and INAF/IAPS), E. Striani (CIFS and INAF/IAPS), M. Cardillo (INAF/OA-Arcetri and INAF/IAPS), F. Gianotti, M. Trifoglio (INAF/IASF-Bo), A. Giuliani, S. Mereghetti, P. Caraveo, F. Perotti (INAF/IASF-Mi), A. Chen (Wits University), A. Argan, E. Costa, E. Del Monte, Y. Evangelista, M. Feroci, F. Lazzarotto, I. Lapshov, L. Pacciani, P. Soffitta, S. Sabatini, V. Vittorini (INAF/IAPS), G. Pucella, M. Rapisarda (ENEA-Frascati), G. Di Cocco, F. Fuschino, M. Galli, C. Labanti, M. Marisaldi (INAF/IASF-Bo), A. Pellizzoni, M. Pilia, A. Trois (INAF/OA-Cagliari), G. Barbiellini, E. Vallazza (INFN Trieste), F. Longo (Univ. Trieste and INFN Trieste), A. Morselli, P. Picozza (INFN and Univ. Roma Tor Vergata), M. Prest (Univ. dell'Insubria), P. Lipari, D. Zanello (INFN and Univ. Roma Sapienza), P. W. Cattaneo, A. Rappoldi (INFN Pavia), S. Colafrancesco (INAF/OAR and Wits University), N. Parmiggiani (University of Modena and Reggio Emilia), A. Ferrari (Univ. Torino and CIFS), A. Antonelli (ASDC and INAF/OAR), P. Giommi (ASDC), L. Salotti, G. Valentini, and F. D'Amico (ASI)
on 1 Aug 2016; 15:26 UT
Credential Certification: Fabrizio Lucarelli (fabrizio.lucarelli@asdc.asi.it)

Subjects: Gamma Ray, >GeV, Neutrinos, Transient

Referred to by ATel #: 9303, 9313, 9315

Following the GCN notice posted by the ICECUBE Collaboration on July 31, 2016, reporting the detection at T0=16/07/31 01:55:04 UT of a very high energy neutrino with reconstructed arrival direction pointing at RA, DEC (J2000)=(214.5440, -0.3347 [deg]) with a 90% containement radius of 45.00 arcmin (stat+sys), we searched for transient gamma-ray emission in the AGILE data above 100 MeV.

Integrating over the 48 hours from 2016-07-29 02:00 UT to 2016-07-31 02:00 UT a maximum likelihood analysis yields a possible detection at a significance level of about 3 sigma with a flux F(E>100 MeV)=(1.5 +/- 0.7)x 10^-06 ph/cm^2/s within the GCN/AMON_ICECUBE_HESE notice error region.

A search backward in time in the AGILE data yields a detection above 4 sigma integrating from 2016-07-28 08:00 UT to 2016-07-30 08:00 UT, with a flux F(E>100 MeV)=(1.7 +/- 0.7) x 10^-06 ph/cm^2/s. The gamma-ray peak of this detection is located at equatorial coordinates (J2000) RA,DEC=(214.48, 0.07 [deg]) +/- 0.8 deg (95% stat. c.l.) +/- 0.1 deg (syst.), Galactic coordinates: l,b=(344.0, 55.9). The AGILE peak location is within one degree from the possible low significance transient source reported by the HAWK Collaboration in the GCN/Circulars #19743.

No significant gamma-ray emission is found following the neutrino event trigger time, and no other known gamma-ray source is found within the AGILE error box.

This measurement was obtained with AGILE observing a large portion of the sky in spinning mode.