Stellar Bubbles as Particle Accelerators: A Case Study of G2.4+1.4

Massive early-type stars, through the interaction of their intense winds with the interstellar medium, generate fast shocks that may accelerate particles to relativistic energies. In 2019, it was reported for the first time the detection of nonthermal emission from a single stellar bubble, G2.4+1.4, powered by a Wolf–Rayet, WR 102. This suggests that massive star winds have the capacity to act as high-energy astrophysical sources. In this study, we apply a complete one-zone model for estimating the nonthermal emission produced by both electrons and protons locally accelerated in a stellar bubble system. For the particular case of G2.4+1.4, we fitted the observations considering that 2.8\% of the wind’s kinetic power is transferred to relativistic electrons, and adopting a magnetic field of 250\,$\mu$G. Additionally, the model was applied for the general case of synthetic O-type stars. It predicts significant gamma-ray emission that, in some cases, may approach the sensitivity limits of current gamma-ray instruments.