Astronomers detect new pulsar wind nebula and its associated pulsar

Astronomers detect new pulsar wind nebula and its associated pulsar
Composite image showcasing the Galactic plane region and Potoroo, featuring the ASKAP total intensity image at 1368 MHz, as well as WISE infrared images at 12 µm and 22 µm. Known Galactic SNRs and HII regions are highlighted, with Potoroo’s position and axis of symmetry marked. Credit: arXiv (2023). DOI: 10.48550/arxiv.2312.06961

Astronomers have made a significant discovery, detecting a new pulsar wind nebula (PWN) and the pulsar that powers it. The findings, presented in a recent paper published on the pre-print server arXiv, were made possible by utilizing the Australian Square Kilometer Array Pathfinder (ASKAP), MeerKAT, and Parkes radio telescopes.

Pulsar wind nebulae (PWNe) are nebulae that are energized by the wind emitted by a pulsar. The pulsar wind consists of charged particles, which, upon interaction with the surrounding environment of the pulsar, particularly the slowly expanding supernova ejecta, give rise to a PWN.

Particles within PWNe gradually lose their energy through radiation as they move away from the central pulsar. Extensive studies of these objects, including X-ray observations and spatially-integrated spectra in the X-ray band, have the potential to provide valuable insights into the flow of particles within these nebulae, offering a deeper understanding of PWNe in general.

In a recent endeavor, a team of astronomers led by Sanja Lazarević from Western Sydney University has discovered a new pulsar wind nebula named “Potoroo” through radio-continuum surveys conducted using ASKAP and MeerKAT. The newly found PWN has been named after a small marsupial native to Australia.

Subsequently, utilizing the Parkes Ultra-Wideband Low (UWL) frequency receiver system, the researchers were able to identify the pulsar candidate, which has been designated as PSR J1638–4713. Further observations of PSR J1638–4713 confirmed its role as the power source for Potoroo.

Observations have revealed that Potoroo displays distinct cometary morphology in both the radio and X-ray bands, indicating that the pulsar leads the PWN and travels through the ambient medium at supersonic speeds.

“For pulsars propelled through the ambient medium at supersonic velocities, the resulting ram pressure shapes the PWN into a bow-shock, confining the pulsar wind in the opposite direction of the pulsar’s motion and giving rise to a cometary-like tail,” explained the authors of the paper.

According to the study, Potoroo is situated at a minimum distance of 32,500 light years and exhibits a radio size of approximately 68.5 light years, while its X-ray size appears to be ten times smaller. As a result, Potoroo possesses the longest radio trails of any known PWN to date.

The results also indicate that Potoroo possesses an unusually steep overall radio spectrum, with a level of -1.27. This value falls below the typical values observed for known PWNe. The astronomers suggest that this steep overall spectral index may be attributed to the interaction between the parent supernova reverse shock and the PWN.

In regard to PSR J1638–4713, it boasts a spin period of 65.74 milliseconds and a dispersion measure of 1,553 pc/cm³, making it the second highest measure among all known radio pulsars. Observations have revealed that PSR J1638–4713 is a young pulsar, with a characteristic age of 24,000 years, a high spin-down luminosity, and a large projected velocity exceeding 1,000 km/s.

More information:
Sanja Lazarević et al, Fast as Potoroo: Radio Continuum Detection of a Bow-Shock Pulsar Wind Nebula Powered by Pulsar J1638-4713, arXiv (2023). DOI: 10.48550/arxiv.2312.06961

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Astronomers detect new pulsar wind nebula and its associated pulsar (2023, December 26)
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