Research led by PhD student Yu Wing Joshua Lee and supervisor Dr Manisha Caleb at the University of Sydney has uncovered the slowest cosmic lighthouse yet – a long-period radio transient – likely a neutron star – spinning once every 6.5 hours.
This discovery, found using CSIRO’s ASKAP radio telescopes and published in Nature Astronomy, not only pushes the boundaries of what we thought possible for such objects, which typically rotate very quickly, but also reveals a rare phenomenon: the ability to see radio pulses from both of the star’s magnetic poles.
The abstract of the paper notes that ASKAP J183950.5−075635.0 boasts the longest known period of this class at six point four five hours. It exhibits emission characteristics of an ordered dipolar magnetic field, with pulsar-like bright main pulses and weaker interpulses offset by about half a period that are indicative of an oblique or orthogonal rotator.
This phenomenon, observed in a long-period radio transient, confirms that the radio emission originates from both magnetic poles and that the observed period corresponds to the rotation period. The spectroscopic and polarimetric properties of the object are consistent with a neutron star origin, and this object is a crucial piece of evidence in our understanding of long-period radio sources and their links to neutron stars.
