Discovery of Perun (G329.9-0.5): A New, Young, Galactic SNR

Abstract

Abstract 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 (ASKAP) Evolutionary Map of the Universe (EMU) survey at 943 MHz, and subsequent follow up observations were conducted with the Australia Telescope Compact Array (ATCA) observatory at 5500 and 9000 MHz. We combine these with additional radio observations from the MeerKAT, Molonglo Observatory Synthesis Telescope (MOST) and MurchisonWidefield Array (MWA) telescopes, infrared (IR) observations from the Spitzer Space Telescope, and X-ray observations from the Chandra X-ray observatory to perform a multi-frequency 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 α = −0.49 ± 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 polarisation at radio frequencies of ∼7–10 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 (SGPS) to perform an H i analysis and estimate a favoured distance range of 6–9 kpc, and thus a favoured age range of ∼70–500 years. We find no high-energy emission in Fermi-LAT data. We detect Perun’s outer shell in 24 μm 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.