The Spectra of IceCube Neutrino (SIN) candidate sources -- IV. Spectral energy distributions and multi-wavelength variability

TL;DR

This study constructs hybrid spectral energy distributions for blazars to investigate their potential as neutrino sources, finding no significant variability differences but a modest gamma-ray/neutrino flux correlation, supporting further lepto-hadronic modeling.

Contribution

It provides the first comprehensive hybrid spectral energy distributions for blazars as neutrino source candidates, including variability analysis and flux correlation assessments.

Findings

No significant variability differences between neutrino candidate and non-candidate blazars.

A 2.2 sigma signal indicating similar gamma-ray and neutrino flux strengths.

Hybrid spectral energy distributions established for future physical modeling.

Abstract

We present hybrid spectral energy distributions, combining photon and neutrino fluxes, for a sample of blazars, which are candidate IceCube neutrino sources. We furthermore check for differences in our sources' variability in the near-infrared, optical, X-ray and $\gamma$-ray bands compared to a sample of non-neutrino source candidate blazars, and investigate the state of each blazar at the arrival time of high-energy neutrinos. We find no significant differences when comparing our sample with control sources, also in terms of their spectral energy distributions, and no correlation between flaring states and neutrino arrival times. Looking for signatures of hadronic production, we check for similar strengths of the $\gamma$-ray and neutrino fluxes and find a $2.2\,\sigma$ signal for our source candidates. The hybrid spectral energy distributions assembled here will form the basis of the next step of our project, namely lepto-hadronic modelling of these blazars to assess the physical likelihood of a neutrino connection.