Galactic Diffuse Gamma-Ray and Neutrino Emission from Cosmic-Ray Interactions in Stellar Atmospheres

TL;DR

This study evaluates the contribution of stellar atmospheres to Galactic diffuse gamma-ray and neutrino backgrounds, finding it negligible at 1 TeV but significant at ultra-high energies, impacting astrophysical source identification.

Contribution

First systematic assessment of stellar atmospheres as a source of diffuse gamma-ray and neutrino emission using coupled stellar evolution and cosmic-ray transport models.

Findings

Stellar contribution to gamma-ray flux at 1 TeV is negligible.

Diffuse neutrino flux from stars is well below IceCube limits.

At energies above 10 TeV, stellar emission surpasses extragalactic backgrounds.

Abstract

The Galactic diffuse gamma-ray emission is conventionally modeled as the product of cosmic-ray interactions with the interstellar medium. However, the cumulative contribution of stellar atmospheres acting as hadronic interaction targets remains an unexplored multi-messenger background. In this work, we present the first systematic evaluation of this stellar diffuse emission by coupling MESA stellar evolution profiles and magnetic-field-modulated cosmic-ray transport with a 3D Galactic population synthesis framework. We find that the cumulative stellar contribution to the Galactic diffuse gamma-ray flux is negligible at 1 TeV, and the associated diffuse neutrino flux ($\sim 10^{-16}\;\mathrm{TeV\;cm^{-2}\;s^{-1}\;sr^{-1}}$) remains orders of magnitude below current IceCube limits. Nevertheless, at ultra-high energies ($>10\;\mathrm{TeV}$), this emission establishes an irreducible local background that overtakes the strongly attenuated extragalactic isotropic gamma-ray background. Our results demonstrate that the Galactic stellar ensemble is a strictly sub-dominant background, indicating that stellar subtraction templates are not required for identifying Galactic PeVatrons or constraining dark matter annihilation.