The Contribution of Stellar Winds to Cosmic Ray Production

TL;DR

Massive stars' stellar winds deposit significant mechanical energy into the interstellar medium, potentially contributing notably to Galactic cosmic ray production, though less than supernova remnants, based on energy estimates and theoretical modeling.

Contribution

This study provides the first comprehensive estimate of the total kinetic energy from stellar winds in the Galaxy and assesses their potential role in cosmic ray production.

Findings

Total stellar wind luminosity in the Galaxy is about 1/4 of supernova explosion power.

Approximately 1-10% of wind energy could convert into Galactic cosmic rays.

Stellar winds may significantly contribute to cosmic ray production, but less than supernova remnants.

Abstract

Massive stars blow powerful stellar winds throughout their evolutionary stages from the main sequence to Wolf-Rayet phases. The amount of mechanical energy deposited in the interstellar medium by the wind from a massive star can be comparable to the explosion energy of a core-collapse supernova that detonates at the end of its life. In this study, we estimate the kinetic energy deposition by massive stars in our Galaxy by considering the integrated Galactic initial mass function and modeling the stellar wind luminosity. The mass loss rate and terminal velocity of stellar winds during the main sequence, red supergiant, and Wolf-Rayet stages are estimated by adopting theoretical calculations and observational data published in the literature. We find that the total stellar wind luminosity due to all massive stars in the Galaxy is about $L_w\approx 1.1\times 10^{41}$ erg/s, which is about 1/4 of the power of supernova explosions, $L_{SN} \approx 4.8\times 10^{41}$ erg/s. If we assume that $\sim 1-10$ % of the wind luminosity could be converted to Galactic cosmic rays (GCRs) through collisonless shocks such as termination shocks in stellar bubbles and superbubbles, colliding-wind shocks in binaries, and bow-shocks of massive runaway stars, stellar winds might be expected to make a significant contribution to GCR production, though lower than that of supernova remnants.