Discovery of Perun (G329.9-0.5): a new, young, Galactic SNR

We present the discovery of possibly the youngest Galactic supernova remnant (SNR) with associated pulsar-wind nebula (PWN), which we name Perun (G329.9-0.5). Perun was serendipitously discovered in the Australian Square Kilometre Array Pathfinder-Evolutionary Map of the Universe survey at 943 MHz, and subsequent follow-up observations were conducted with the Australia Telescope Compact Array observatory at 5500 and 9000 MHz. We combine these with additional radio observations from the MeerKAT, Molonglo Observatory Synthesis Telescope, and Murchison Widefield Array telescopes, infrared (IR) observations from the SpitzerSpace Telescope, and X-ray observations from the Chandra X-ray observatory to perform a multifrequency analysis. The radio morphology shows a small angular size shell (D = 70 arcsec) with a luminous, central PWN. We measure a total spectral index of $\alpha = -0.49\pm 0.05$, which should be typical for a young, composite SNR. Crucial evidence for Perun's SNR classification comes from the detection of linear fractional polarization at radio frequencies of $\sim$7 per cent-10 per cent with both radial and tangential orientations, similar to the young SNR G1.9+0.3. We use data from the Southern Galactic Plane Survey to perform an H I analysis and estimate a favoured distance range of 6-9 kpc, and thus a favoured age range of $\sim$70-500 yr. We find no high-energy emission in Fermi-Large Area Telescope data. We detect Perun's outer shell in 24 $\mu$m indicating the possible presence of [O IV] and [Fe III] emission, also typical for young SNRs. Overall, these observations and analysis confirm Perun as a young, Galactic SNR with a prominent PWN.