G11.2-0.3: The Young Remnant of a Stripped-Envelope Supernova

TL;DR

This study presents a detailed analysis of the young supernova remnant G11.2-0.3, revealing its age, structure, and likely progenitor type, through extensive X-ray observations and morphological assessments.

Contribution

It provides new measurements of the remnant's expansion rate, age, and morphology, and proposes a novel origin scenario involving a stripped-envelope progenitor and anisotropic circumstellar medium.

Findings

G11.2-0.3 is approximately 1400-2400 years old.

The remnant shows high absorption, ruling out association with the 386 CE supernova.

The morphology suggests a stripped-envelope progenitor with anisotropic wind or binary interaction.

Abstract

We present results of a 400-ks Chandra observation of the young shell supernova remnant (SNR) G11.2-0.3, containing a pulsar and pulsar-wind nebula (PWN). We measure a mean expansion rate for the shell since 2000 of 0.0277+/-0.0018% per yr, implying an age between 1400 and 2400 yr, and making G11.2-0.3 one of the youngest core-collapse SNRs in the Galaxy. However, we find very high absorption ($A_V \sim 16^m \pm 2^m$), confirming near-IR determinations and ruling out a claimed association with the possible historical SN of 386 CE. The PWN shows strong jets and a faint torus within a larger, more diffuse region of radio emission and nonthermal X-rays. Central soft thermal X-ray emission is anticorrelated with the PWN; that, and more detailed morphological evidence, indicates that the reverse shock has already reheated all ejecta and compressed the PWN. The pulsar characteristic energy-loss timescale is well in excess of the remnant age, and we suggest that the bright jets have been produced since the recompression. The relatively pronounced shell and diffuse hard X-ray emission in the interior, enhanced at the inner edge of the shell, indicate that the immediate circumstellar medium into which G11.2-0.3 is expanding was quite anisotropic. We propose a possible origin for G11.2-0.3 in a stripped-envelope progenitor that had lost almost all its envelope mass, in an anisotropic wind or due to binary interaction, leaving a compact core whose fast winds swept previously lost mass into a dense irregular shell, and which exploded as a Type cIIb or Ibc supernova.