2025/04/22 by Saikat Das, Das, Saikat, Srijita Hazra +3 · 1 voice · 3 citations
Physics and Astronomy · #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE)
paper · doi:10.48550/arxiv.2504.16019
The detection of the Amaterasu event of energy 244 EeV by the Telescope Array, one of the most energetic ultrahigh-energy cosmic rays (UHECRs; E\gtrsim0.1 EeV) observed to date, invites scrutiny of its potential source. We investigate whether the nearby blazar PKS~1717+177 at redshift z=0.137, located within 2.5^∘ of the reconstructed arrival direction, could explain the event under a proton-primary hypothesis. Using a one-zone jet model, we fit the multiwavelength spectral energy distribution of the source, incorporating both leptonic and hadronic cascade emissions from photohadronic interactions inside the jet. Our model supports a cosmic-ray origin of the very-high-energy (εγ\gtrsim 100 GeV) γ-ray flux and predicts a subdominant neutrino flux, one order of magnitude lower than from TXS~0506+056. Under Lorentz invariance violation, UHECRs escaping the blazar jet above a specific energy can propagate unattenuated over hundreds of Mpc due to an increase in energy loss length for certain parameter choices. In such a scenario, the Amaterasu event can have a plausible origin from this blazar. Our analysis indicates negligible deflection in the Galactic magnetic field, implying a strong extragalactic magnetic field is required. Our findings provide a compelling multimessenger framework linking UHECRs, γ-rays, and neutrinos and motivate targeted searches by current and future high-energy neutrino telescopes during increased γ-ray or X-ray activity of this blazar.