Hadronic vs leptonic models for $\gamma$-ray emission from VER J2227+608

TL;DR

This paper compares leptonic and hadronic models for gamma-ray emission from VER J2227+608, analyzing spectral features and predicting different high-energy behaviors to guide future observations.

Contribution

It provides a detailed analysis of both leptonic and hadronic scenarios for the gamma-ray emission, highlighting how spectral features can distinguish between the models.

Findings

Leptonic model explains the spectral break via electron energy loss and matches radio/X-ray data.

Hadronic model attributes the break to ion diffusion, constraining the diffusion coefficient.

Future observations above 100 TeV can differentiate the models based on spectral predictions.

Abstract

Recent observations of VER J2227+608 reveal a broken power $\gamma$-ray spectrum with the spectral index increasing from $\sim 1.8$ in the GeV energy range to $\sim 2.3$ in the TeV range. Such a spectral break can be attributed to radiative energy loss of energetic electrons in the leptonic scenario for the $\gamma$-ray emission, which, in combination with characteristic age of the nearby pulsar, can be used to constrain magnetic field in the emission region. We show that the radio and X-ray observations can also be explained in such a scenario. In the hadronic scenario, the spectral break can be attributed to diffusion of energetic ions in a turbulent medium and detailed spectral measurement can be used to constrain the diffusion coefficient. These two models, however, predict drastically different spectra above 100 TeV, which will be uncovered with future high-resolution observations, such as LHAASO and/or CTA.