Jing et al. report the observations of the radio shell of the supernova remnant (SNR) G310.6–1.6 at 943 MHz from the Evolutionary Map of the Universe (EMU) and the Polarization Sky Survey of the Universe’s Magnetism (POSSUM) surveys by using the Australian Square Kilometre Array Pathfinder (ASKAP). We detect polarized emission from the central pulsar wind nebula (PWN) with rotation measures varying from –696 rad m⁻² to –601 rad m⁻². We measure the integrated flux density of the shell to be 36.4 ± 2.2 mJy at 943 MHz and derive a spectral index of α_pwn = −0.4 ± 0.1 for the PWN and α_shell = −0.7 ± 0.3 for the SNR shell. From the combined radio and X-ray observations, the object can be identified as a supernova explosion of about 2500 yr ago with an energy of about 1.3 × 10⁵⁰ erg, suggesting an ejected mass of about 10 M_⊙. The circular radio shell outside the circular hard X-ray shell is unique among Galactic SNRs. We discuss several possible scenarios, including blast wave, reverse shock, and pulsar-fed emission, but find that none of them can fully explain the observed characteristics of the shell. This poses a challenge for understanding the evolution of SNRs. The results of this paper demonstrate the potential of the ASKAP EMU and POSSUM surveys to discover more objects of small angular size and low surface brightness.

The figures above illustrate the following: Left: ASKAP MFS Stokes I image at 943 MHz with an angular resolution of 12“. 4, shown by the orange circle in the bottom-right-hand corner. Middle: Chandra X-ray photon image averaged across the 1.0–8.0 keV band with an angular resolution of 0“. 5. Right: the same as the middle panel, but with the X-ray image smoothed to 12“. 4. All contours show the ASKAP Stokes I in the levels of 5σ × 2ⁱ, i = 0, …, 5 with the rms noise σ of 30 μJy beam⁻¹. The cyan cross indicates the position of PSR J1400–6325.