Clumping effects on non-thermal particle spectra in massive star systems

TL;DR

This paper investigates how wind clumping in massive star systems affects the spectra of non-thermal particles, revealing flux variability and spectral shifts linked to clump properties and energy processes.

Contribution

It introduces a model for the impact of wind clumpiness on relativistic particle spectra in colliding wind systems, considering acceleration and energy losses.

Findings

Clumpy winds cause flux variations in particle spectra.

Spectral features shift from low to high energies over time.

Variability depends on clump size, filling factor, and energy loss processes.

Abstract

Observational evidence exists that winds of massive stars are clumped. Many massive star systems are known as non-thermal particle production sites, as indicated by their synchrotron emission in the radio band. As a consequence they are also considered as candidate sites for non-thermal high-energy photon production up to gamma-ray energies. The present work considers the effects of wind clumpiness expected on the emitting relativistic particle spectrum in colliding wind systems, built up from the pool of thermal wind particles through diffusive particle acceleration, and taking into account inverse Compton and synchrotron losses. In comparison to a homogeneous wind, a clumpy wind causes flux variations of the emitting particle spectrum when the clump enters the wind collision region. It is found that the spectral features associated with this variability moves temporally from low to high energy bands with the time shift between any two spectral bands being dependent on clump size, filling factor, and the energy-dependence of particle energy gains and losses.