A Novel Parameterization for Rapid Cooling in Supernova Remnants, with applications to the Pa 30 nebula

TL;DR

This paper introduces a new parameterization for rapid cooling in supernova remnants, explaining the formation of filamentary structures like those observed in Pa 30 and linking cooling timescales to morphological features.

Contribution

It proposes a singular cooling parameter $eta$ to characterize supernova remnant morphologies and explains filament formation through Rayleigh-Taylor instabilities influenced by rapid cooling.

Findings

Filamentary structures form when $eta extgreater 400$, with cooling times shorter than 1/400 of Sedov time.

Ejecta in these filaments move ballistically at 95-100% of free expansion speed.

Estimated explosion energy for rapid cooling remnants is approximately 3.5 x 10^{47} erg.

Abstract

We systematically study how cooling creates structural changes in supernova remnants as they evolve. Inspired by the peculiar morphology of the Pa 30 nebula, we adopt a framework in which to characterize supernova remnants under different degrees of cooling. Our cooling framework characterizes remnants with a singular parameter called $\beta$ that sets how rapidly the system's thermal energy is radiated or emitted away. A continuum of morphologies is created by the implementation of different cooling timescales. For $\beta \gtrsim 400$, or when the cooling timescale is shorter than $\approx \frac{1}{400}$ of the Sedov time, the ejecta is shaped into a filamentary structure similar to Pa 30. We explain the filament creation by the formation of Rayleigh-Taylor Instability fingers where cooling has prevented the Kelvin-Helmholtz Instability from overturning and mixing out the tips. The ejecta in these filaments have not decelerated and are moving almost completely ballistically at $\approx 95-100\%$ their free expansion speed. In this rapid cooling regime, an explosion energy $\approx 3.5 \times 10^{47}$ erg is inferred. We also propose the cooling mechanism required to create these structures necessitates removing energy at a rate of $2\%$ of $E_{\rm ej}/t$, which implies a cooling luminosity of $\approx 10^{36}$ erg/s.