Super-luminous X-ray Emission from the Interaction of Supernova Ejecta with Dense Circumstellar Shells

TL;DR

This paper explores how supernova ejecta interacting with dense circumstellar shells can produce extremely luminous X-ray emissions, potentially rivaling optical super-luminous supernovae in energy output.

Contribution

It provides a theoretical framework and simple expressions for X-ray luminosity from supernova shocks interacting with dense circumstellar shells, highlighting conditions for high luminosity and different cooling regimes.

Findings

X-ray luminosities can reach 10^44-10^45 erg/s with normal supernova energies.

Hard X-rays can penetrate dense shells and ionize material, reducing absorption.

Luminosity peaks after shock traverses the entire circumstellar shell.

Abstract

For supernova powered by the conversion of kinetic energy into radiation due to the interactions of the ejecta with a dense circumstellar shell, we show that there could be X-ray analogues of optically super-luminous SNe with comparable luminosities and energetics. We consider X-ray emission from the forward shock of SNe ejecta colliding into an optically-thin CSM shell, derive simple expressions for the X-ray luminosity as a function of the circumstellar shell characteristics, and discuss the different regimes in which the shock will be radiative or adiabatic, and whether the emission will be dominated by free-free radiation or line-cooling. We find that even with normal supernova explosion energies of 10^51 erg, there exists CSM shell configurations that can liberate a large fraction of the explosion energy in X-rays, producing unabsorbed X-ray luminosities approaching 10^44 erg/s events lasting a few months, or even 10^45 erg/s flashes lasting days. Although the large column density of the circumstellar shell can absorb most of the flux from the initial shock, the most luminous events produce hard X-rays that are less susceptible to photoelectric absorption, and can counteract such losses by completely ionizing the intervening material. Regardless, once the shock traverses the entire circumstellar shell, the full luminosity could be available to observers.