ANTARES search for neutrinos from TXS0506+056,
reported as a source of high-energy neutrinos
by the IceCube Neutrino Observatory

[Published July 12th, 2018]

Two papers published this week in the journal Science have for the first time provided evidence for a known blazar as a source of high-energy neutrinos detected by the IceCube observatory. The papers are available at this address and here. This blazar, designated by astronomers as TXS 0506+056, was first singled out following a neutrino alert sent by IceCube on Sept. 22, 2017 (IC170922A). More information are given on the IceCube website (see also the Press Conference).

Thanks to sharing of information by the IceCube collaboration before the public release, the ANTARES Collaboration was able to perform three different searches for neutrino candidates associated with IC170922A or from the direction of TXS 0506+056. The first one refers to the online follow-up associated with IC170922A. The second is based on the standard likelihood method employed by the Collaboration to search for point-like neutrino sources. The third uses the information from the time-dependent analysis performed by the IceCube collaboration, which reports a bursting activity centered on December 13, 2014, as input for an ANTARES dedicated analysis. The results of these searches are presented in an article submitted to The Astrophysical Journal, available here and on arXiv. The online follow-up and the time-dependent analysis yield no events related to the source. The time-integrated study performed over a period from 2007 to 2017 fits 1.03 signal events, which corresponds to a p-value of 3.4%. TXS 0506+056 consequently appears as the third most significant source among the 107 scrutinised by ANTARES. Accounting for all trials, the p-value rises up to 87%.

Left : a blazar is accelerating protons that produce pions, which produce neutrinos and gamma rays. Neutrinos are always the result of a hadronic reaction such as the one displayed here. Gamma rays can be produced in both hadronic and electromagnetic interactions (Credit : IceCube/NASA). Right : a high-energy neutrino detected by IceCube on Sept. 22, 2017, with an estimated energy of 290 TeV. The neutrino event display shows a muon, created by the interaction of a neutrino with the ice very close to IceCube, which leaves a track of light while crossing the detector. In this display, the light collected by each sensor is shown with a colored sphere. The color gradient, from red to green/blue, shows the time sequence (Credit: IceCube Collaboration).

Distribution of ANTARES events in the (RA, DEC) coordinates around the position of TXS 0506+056. The inner (outer) green line depicts the one (five) degree distance from the position source location, indicated as a gray star. The red point denotes a shower-like event, whereas the blue points indicate track-like events. The dashed circles around the events indicate the angular error estimate. Different shades of red and blue correspond to the values assumed by the energy estimators, the right legend shows the color scales. The number of hits is used for shower-like events and a parameter ρ for track-like events.

The ANTARES Collaboration thanks the IceCube Collaboration for the sharing of information before the public release. ANTARES congratulates the IceCube Collaboration for what seems to be a new major step forward in the multi-messenger era !