Slowest Radio Pulsar Found in Small Magellanic Cloud

A new radio pulsar, PSR J0103-72, has been discovered in the Small Magellanic Cloud through a reanalysis of archival Parkes/Murriyang observations. The discovery, detailed in a paper by Weiyu Wang and Rahul Sengar, was submitted to arXiv on 8 October 2026.

PSR J0103-72 has a spin period of 1.327 seconds, making it the slowest known radio pulsar in the Small Magellanic Cloud. Its dispersion measure is 272 ± 13 pc cm⁻³, the second highest known there. After subtracting the predicted Galactic foreground, the remaining dispersion measure contribution is approximately 230 to 242 pc cm⁻³. This may indicate a long path through the ionised medium of the Small Magellanic Cloud, enhanced ionised gas along the sightline, or both.

The observations originally targeted supernova remnants and pulsar-wind nebulae in the Small Magellanic Cloud. Two pulsars had previously been identified in these data, and PSR J0103-72 is the third, independently detected in two observations of its target field. No plausible supernova remnant or pulsar-wind nebula was found to be associated with the pulsar.

Although the data had been searched using both FFT and fast folding algorithms before, the new FFT-based reprocessing identified PSR J0103-72 from a candidate with weak Fourier-domain significance. This suggests that such candidates can reveal faint, narrow-duty-cycle pulsars that were missed in earlier extragalactic searches.

Sourcearxiv.org