6695 1807.05201 10.1140/epjc/s10052-019-6695-6 185 7 Constraints on differential Shapiro delay between neutrinos and photons from IceCube-170922A Regular Article - Theoretical Physics 1 4 2019 2 21 2018 10 1 2019 2 18 2019 3 1 The Author(s) 2019 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Funded by SCOAP3 Sibel Boran borans@itu.edu.tr Shantanu Desai shantanud@iith.ac.in Emre O. Kahya eokahya@itu.edu.tr 0000 0001 2174 543X grid.10516.33 Department of Physics Istanbul Technical University Maslak Istanbul 34469 Turkey Department of Physics Indian Institute of Technology Hyderabad Telangana 502285 India Abstract On 22nd September 2017, the IceCube Collaboration detected a neutrino with energy of about 290 TeV from the direction of the gamma-ray blazar TXS 0506+056, located at a distance of about 1.75 Gpc. During the same time, enhanced gamma-ray flaring was also simultaneously observed from multiple telescopes, giving rise to only the second coincident astrophysical neutrino/photon observation after SN 1987A. We point out that for this event, both neutrinos and photons encountered a Shapiro delay of about 6300 days along the way from the source. From this delay and the relative time difference between the neutrino and photon arrival times, one can constrain violations of Einstein’s Weak Equivalence Principle (WEP) for TeV neutrinos. We constrain such violations of WEP using the Parameterized Post-Newtonian (PPN) parameter γ, which is given by |γν-γEM|<5.5×10-2, after assuming time difference of 175 days between neutrino and photon arrival times.