Revisiting the Supernova Engines in the 3C 397 and W49B Supernova Remnants

TL;DR

This study uses spatially resolved X-ray spectroscopy to analyze supernova remnants 3C 397 and W49B, comparing observed elemental abundances with models to infer their explosion types and energies, revealing complex origins and the limitations of current diagnostics.

Contribution

It provides a detailed spectroscopic analysis of two SNRs, comparing observed abundances with diverse nucleosynthesis models, and highlights the complexities in supernova classification.

Findings

W49B's composition aligns with thermonuclear origin.

Both remnants likely resulted from low-energy supernovae (~10^{50} erg).

Fe/Si and Ca/Si ratios suggest thermonuclear models, but no model fully matches observations.

Abstract

The nature of the supernova remnants (SNRs) 3C 397 and W49B has long been a subject of debate, with prior studies offering conflicting interpretations between thermonuclear and core-collapse scenarios. To help settle this debate, we present a systematic, spatially resolved, spectroscopic analysis of both remnants using XMM-Newton. By applying multi-component thermal models, we derive key physical properties including elemental abundances, ejecta temperatures, ambient densities, and explosion energetics. We compare the inferred metal abundance ratios to a wide range of core-collapse and thermonuclear nucleosynthesis models, including new models whose explosion energies differ from the canonical value of $10^{51}$ ergs. We find that the observed Fe/Si and Ca/Si ratios in both SNRs are best matched by certain thermonuclear models. However, no model fully reproduces the complete set of observed abundance patterns. In 3C 397, high Fe enrichment and spatial abundance variations suggest interaction with a dense progenitor environment, and W49B's composition is overall consistent with a thermonuclear origin; however both require a low energy ($\sim 10^{50}$ erg) supernova explosion. We additionally map the Fe K$\alpha$ line centroid energies and find a spread, with W49B falling within the core-collapse region -- highlighting both environmental complexity and the limitations of this diagnostic for supernova classification. Our results highlight the need for caution in relying on any single diagnostic or nucleosynthesis model for supernova typing, underscore the need for improved nucleosynthesis models, and motivate future high-resolution, high-throughput observations.