Core-collapse supernovae in dense environments -- particle acceleration and non-thermal emission

Abstract

Supernova remnants are known to accelerate cosmic-rays from the detection of non-thermal emission in radio waves, X-rays, and gamma-rays. However, the ability to accelerate cosmic-rays up to PeV energies has yet to be demonstrated. The presence of cut-offs in the gamma-ray spectra of several young SNRs led to the idea that PeV energies might only be achieved during the first years of a remnant's evolution. We use our time-dependent acceleration-code RATPaC to study the acceleration of cosmic-rays in supernovae expanding into dense environments around massive stars. We performed spherically symmetric 1-D simulations in which we simultaneously solve the transport equations for cosmic-rays, magnetic turbulence, and the hydrodynamical flow of the thermal plasma in the test-particle limit. We investigated typical CSM parameters expected around RSG and LBV stars for freely expanding winds and accounted for the strong gamma-gamma-absorption in the first days after explosion. The maximum achievable particle energy is limited to below 600TeV even for largest considered values of the magnetic field and mass-loss rates. The maximum energy is not expected to surpass 200TeV and 70TeV for LBVs and RSGs that experience moderate mass-loss prior to the explosion. We find gamma-ray peak-luminosities consistent with current upper limits and evaluated that current-generation instruments are able to detect the gamma-rays from Type-IIP explosions at distances up to 60kpc and Type-IIn explosions up to 1.0Mpc. We also find a good agreement between the thermal X-ray and radio synchrotron emission predicted by our models with a range of observations.