HFPK 334: An unusual Supernova Remnant in the Small Magellanic Cloud

TL;DR

This study presents multi-wavelength observations of the unusual supernova remnant HFPK 334 in the Small Magellanic Cloud, revealing its shell morphology, a likely background X-ray source, and properties indicative of a young age and magnetic field.

Contribution

First detailed multi-wavelength analysis of HFPK 334, providing insights into its morphology, age, and magnetic environment, highlighting its status as a young SNR in a low-density region.

Findings

Remnant exhibits shell morphology with a size of ~20 pc.

Central X-ray source likely a background object.

Estimated age of less than 1800 years.

Abstract

We present new Australia Telescope Compact Array (ATCA) radio-continuum and XMM-Newton/Chandra X-ray Observatory (CXO) observations of the unusual supernova remnant HFPK 334 in the Small Magellanic Cloud (SMC). The remnant follows a shell type morphology in the radio-continuum and has a size of $\sim$20~pc at the SMC distance. The X-ray morphology is similar, however, we detect a prominent point source close to the center of the SNR exhibiting a spectrum with a best fit powerlaw with a photon index of $\Gamma = 2.7 \pm 0.5$. This central point source is most likely a background object and cannot be directly associated with the remnant. The high temperature, nonequilibrium conditions in the diffuse region suggest that this gas has been recently shocked and point toward a younger SNR with an age of $\lesssim 1800$ years. With an average radio spectral index of $\alpha=-0.59\pm0.09$ we find that an equipartition magnetic field for the remnant is $\sim$90~$\mu$G, a value typical of younger SNRs in low-density environments. Also, we report detection of scattered radio polarisation across the remnant at 20~cm, with a peak fractional polarisation level of 25$\pm$5\%.