New radio continuum study of the Large Magellanic Cloud Supernova Remnant N49

TL;DR

This study provides new radio and X-ray observations of the Large Magellanic Cloud's supernova remnant N49, revealing a 'bullet' feature, its properties, and magnetic field characteristics, enhancing understanding of SNR morphology and evolution.

Contribution

The paper introduces new ATCA radio observations combined with Chandra X-ray data, identifying a 'bullet' feature and analyzing its dynamics, polarization, and magnetic properties, which were not previously documented.

Findings

Identification of a 'bullet' feature with an estimated velocity of 1300 km/s.

Radio spectral index of -0.55 indicating middle-age SNR.

Polarisation levels higher than previous studies, with mean fractional polarisation of 7-10%.

Abstract

We present new Australia Telescope Compact Array (ATCA) radio observations toward N49, one of the brightest extragalactic Supernova remnants (SNRs) located in the Large Magellanic Cloud. Our new and archival ATCA radio observations were analysed along with $Chandra$ X-ray data. These observations show a prominent `bullet' shaped feature beyond the southwestern boundary of the SNR. Both X-ray morphology and radio polarisation analysis support a physical connection of this feature to the SNR. The 'bullet' feature's apparent velocity is estimated at $\sim$1300 km s$^{-1}$, based on its distance ($\sim$10 pc) from the remnant's geometric centre and estimated age ($\sim$7600 yrs). we estimated the radio spectral index, $\alpha= -0.55 \pm 0.03$ which is typical of middle-age SNRs. Polarisation maps created for N49 show low to moderate levels of mean fractional polarisation estimated at 7$\pm$1% and 10$\pm$1% for 5.5 and 9 GHz, respectively. These values are noticeably larger than found in previous studies. Moreover, the mean value for the Faraday rotation of SNR N49 from combining CABB data is 212$\pm$65 rad m$^{-2}$ and the maximum value of RM is 591$\pm$103 rad m$^{-2}$.