Testing unified models for the origin of ultrahigh-energy cosmic rays and neutrinos: Multimessenger approaches with x-ray observations

TL;DR

This paper explores the role of x-ray transient objects as sources of ultrahigh-energy cosmic rays and neutrinos, using multimessenger observations to constrain source models and parameters.

Contribution

It develops a generic model linking x-ray emissions with high-energy neutrino production, providing new constraints on source characteristics for UHECRs and neutrinos.

Findings

X-ray transients are likely sources if photomeson production dominates.

Multimessenger observations constrain source parameters like magnetic field and Lorentz factor.

Current and future x-ray facilities can test unified models of UHECR and neutrino origins.

Abstract

The unified models of astrophysical sources to account for ultrahigh-energy cosmic rays (UHECRs) and high-energy cosmic neutrinos with energies greater than 100 TeV have been discussed. Based on model-independent arguments, we argue that if the photomeson production is the dominant mechanism, the most probable candidate sources are x-ray transient objects, allowing for the semi-transparency for the photomeson production. We develop a generic model of high-energy neutrino emitters accompanied by x-ray emission, and present how multimessenger observations can place significant constraints on the source parameters that characterize the common sources of neutrinos and UHECRs, such as the cosmic-ray loading factor. The requirements of UHECR acceleration, escape, and energetics further constrain the magnetic field and the bulk Lorentz factor of the sources. The resulting bounds provide diagnoses of the unified models, which demonstrates the importance of current and future x-ray facilities such as MAXI and Einstein Probe.