Astronomers hailing from Western Sydney University in Australia, in collaboration with other institutions, have unveiled a groundbreaking discovery: the detection of a new pulsar wind nebula (PWN) and the pulsar driving its existence. The findings, detailed in a paper published on the arXiv pre-print server on Dec. 12, were made possible through the deployment of cutting-edge technology, including the Australian Square Kilometer Array Pathfinder (ASKAP), MeerKAT, and Parkes radio telescopes.
Pulsar wind nebulae are cosmic phenomena energized by the winds emitted from pulsars. These winds, comprised of charged particles, collide with the pulsar's surroundings, creating a PWN—particularly when interacting with the slowly expanding remnants of a supernova. The particles within PWNe undergo energy loss through radiation, leading to a decrease in energy levels with increasing distance from the central pulsar. Comprehensive studies, spanning multiple wavelengths and incorporating X-ray observations, have the potential to yield crucial insights into the dynamics of these nebulae, shedding light on their fundamental nature.
The team, spearheaded by Sanja Lazarević from Western Sydney University, identified a new PWN named “Potoroo” in radio-continuum surveys conducted with ASKAP and MeerKAT. The PWN derives its name from a small marsupial native to Australia. Subsequent observations using the Parkes Ultra-Wideband Low frequency receiver system pinpointed the associated pulsar, designated as PSR J1638–4713, confirming its role as the powerhouse behind Potoroo.
The observations unveiled distinctive cometary morphology in both radio and X-ray bands, indicating that Potoroo is led by the pulsar, which traverses the ambient medium at supersonic speeds. The interaction results in a bow-shock configuration, with the PWN confined in the opposite direction to the pulsar's motion, forming a tail reminiscent of a comet.
Notably, Potoroo's location lies at a distance of at least 32,500 light years, boasting radio trails that extend over an impressive 68.5 light years—setting a record for the longest PWN radio trails known to date. Intriguingly, its X-ray size appears to be ten times smaller than its radio counterpart.
Analyzing Potoroo's characteristics, astronomers found an unusually steep overall radio spectrum with a level of -1.27, below typical values for known PWNe. The team postulates that this steep spectral index may result from the interaction between the parent supernova reverse shock and the PWN.
Turning attention to PSR J1638–4713, the pulsar exhibits a spin period of 65.74 milliseconds and a dispersion measure of 1,553 pc/cm3—ranking as the second highest among all known radio pulsars. This young pulsar, with a characteristic age of 24,000 years, possesses a high spin-down luminosity and an impressive projected velocity exceeding 1,000 km/s.