Particle acceleration in supernova remnant expanding inside wind-blown bubble

Abstract

CONTEXT: Supernova Remnants (SNRs) are considered as the primary sources of galactic cosmic rays (CRs), where CRs are assumed to be accelerated by diffusive shock acceleration (DSA) mechanism. The SNR shocks expand in the complex ambient environment, particularly in the core-collapse scenarios as those SNRs evolve inside wind-blown bubbles created by the mass-loss of massive stars. Therefore, the evolution of core-collapse SNRs, as well as CRs acceleration is expected to be considerably different from SNR evolution in a uniform environment. AIM: The aim is to observe the influence of different ambient medium of core-collapse SNR shock on the particle spectra. Furthermore, the interactions of SNR shock with fluctuations in density within the wind-blown bubble generate several transmitted and reflected shocks. So, the impact of SNR shock interactions with different discontinuities, on particle spectra, and finally the effect on emission from the remnant are also the areas of focus. Methods. The hydrodynamic structures of wind-blown bubbles at pre-supernova stages formed by $20M_{\odot}$, $35M_{\odot}$, and $60M_{\odot}$ stars have been used to create the ambient environment for SNRs. Evolution of those stars through different stages from Zero Age Main Sequence (ZAMS) to the pre-supernova stage, results into formation of structurally different wind bubbles. Then, the transport equation for cosmic rays, and hydrodynamic equations have been solved simultaneously in 1-D spherical symmetry. RESULT: The modifications in particle spectra depend on the hydrodynamics and magnetic field structure of SNR ambient medium. We have obtained softer spectra with spectra index close to 2.5 originated during SNR interaction with hot wind bubble and further, magnetic field structure effectively influences the emission morphology of SNR as it governs the transportation of particles.