Letter to the Editor

Repeated pattern of γ-ray flares in the blazar PKS 1502+106 coincident with the IC190730A neutrino event

Growing evidence of structured jets as neutrino sources

¹ Institute of Astrophysics, Foundation for Research and Technology-Hellas, GR-70013 Heraklion, Greece
² Department of Physics, University of Crete, GR-70013 Heraklion, Greece
³ St. Petersburg University, 7/9 Universitetskaya nab., St.Petersburg 199034, Russia

^⋆ Corresponding author; blinov@ia.forth.gr

Received: 9 December 2024
Accepted: 27 January 2025

Abstract

Context. It has been demonstrated that at least 10% of the brightest blazars in the fourth Fermi-LAT catalog of γ-ray sources exhibit repeating patterns of γ-ray flares. These events may be associated with the presence of a non-uniform sheath surrounding a fast jet spine in some blazars. Theoretical models suggest that such a sheath could facilitate neutrino production in these structured jets.

Aims. We aim to test the marginal statistical evidence previously reported for a connection between repeating patterns of γ-ray flares in blazars and high-energy neutrino events that are positionally consistent with these sources.

Methods. We identified a repeating pattern of flares in the γ-ray light curve of the blazar PKS 1502+106, which lies within the 50% uncertainty region of the IC190730A neutrino candidate event. This occurrence is combined with two other high-energy (≥200 TeV) neutrino events from ICECAT-1, which arrived in both positional and temporal coincidence with two blazars exhibiting ongoing repeating flare patterns. We conducted a Monte Carlo simulation to evaluate the likelihood of accidental coincidences between the repeating flare patterns and neutrino events, accounting for potential unrecognized systematic uncertainties in the arrival directions of the ICECAT-1 events.

Results. Our findings indicate the probability of a random coincidence, in both time and arrival direction for three high-energy neutrino candidates and three blazars with ongoing recurring patterns of γ-ray flares, is 1.56 × 10⁻³ (3.2σ).