Multi-epoch leptohadronic modeling of neutrino source candidate blazar PKS 0735+178

¹ Ruhr University Bochum, Faculty of Physics and Astronomy, Astronomical Institute (AIRUB), Universitätsstraße 150, 44801 Bochum, Germany
² Weizmann Institute of Science, Department of Particle Physics and Astrophysics, Herzl Street 234, 76100 Rehovot, Israel
³ Finnish Centre of Astronomy with ESO (FINCA), University of Turku, FI-20014 Turku, Finland
⁴ Aalto University Metsähovi Radio Observatory, Metsähovintie 114, 02540 Kylmälä, Finland
⁵ Deutsches Elektronen-Synchrotron DESY, Platanenallee 6, D-15738 Zeuthen, Germany
⁶ Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland
⁷ Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
⁸ Aalto University Department of Electronics and Nanoengineering, P.O. BOX 15500, FI-00076 Aalto, Finland

^⋆ Corresponding author; omeliukh@astro.rub.de

Received: 6 September 2024
Accepted: 23 February 2025

Abstract

Context. The origin of the astrophysical neutrino flux discovered by IceCube remains largely unknown. Several individual neutrino source candidates were observed. Among them is the gamma-ray flaring blazar TXS 0506+056. A similar coincidence of a high-energy neutrino and a gamma-ray flare was found in blazar PKS 0735+178.

Aims. By modeling the spectral energy distributions of PKS 0735+178, we aimed to explore the physical conditions that lead to neutrino production at different stages of the source's activity.

Methods. We analyzed the multiwavelength data from the selected time periods. Using numerical simulations of radiation processes in the source, we explored the parameter space of one-zone leptonic and leptohadronic models to find the best-fit solutions that explain the observed photon fluxes.

Results. We demonstrated how model parameter degeneracy affected the prediction of neutrino spectra. We showed that the available multiwavelength data were insufficient to predict the neutrino spectrum unambiguously. However, under the condition of neutrino rates maximization, we proposed a scenario in which 0.1 neutrino events were produced during the 50-day flare.