High-Energy Emission from Interacting Supernovae: New Constraints on Cosmic-Ray Acceleration in Dense Circumstellar Environments

Supernovae (SNe) with strong interactions with circumstellar material (CSM) are promising candidate sources of high-energy neutrinos and gamma-rays and have been suggested as an important contributor to Galactic cosmic rays (CRs) beyond 1015 eV. Taking into account the shock dissipation by a fast velocity component of SN ejecta, we present comprehensive calculations of the nonthermal emission from SNe powered by shock interactions with a dense wind or CSM. Remarkably, we consider electromagnetic cascades in the radiation zone and subsequent attenuation in the pre-shock CSM. A new time-dependent phenomenological prescription provided by this work enables us to calculate gamma-ray, hard X-ray, radio, and neutrino signals, which originate from CRs accelerated by the diffusive shock acceleration (DSA) mechanism. We apply our results to Type IIn SN 2010jl and Type Ib/IIn SN 2014C, for which the model parameters can be determined from the multiwavelength data. For SN 2010jl, the more promising case, by using the the latest Fermi Large Area Telescope Pass 8 data release, we derive new constraints on the CR energy fraction, ϵ p ≲ 0.05–0.1. We also find that the late-time radio data of these interacting SNe are consistent with our model. Further multimessenger and multiwavelength observations of nearby interacting SNe should give us new insights into the DSA in dense environments, as well as pre-SN mass-loss mechanisms