South Africa’s MeerKAT radio telescope array has again proven its worth with yet another unprecedented discovery: what appears to be an unusually slowly rotating radio-emitting neutron star. The discovery was made, using MeerKAT data, by a research team based at the University of Manchester in the UK. The team is named the More Transients and Pulsars group, abbreviated to MeerTRAP, and it is funded by the European Research Council (with which the UK is ‘associated’, following its departure from the European Union).

The discovery also involved another group of scientists doing astrophysical research using MeerKAT data, the University of Cape Town in South Africa-led international ThunderKAT group. ThunderKAT is an acronym for The HUNt for Dynamic and Explosive Radio transients with meerKAT.

The discovery of this unusual neutron star was made by the MeerTRAP team while they were ‘piggybacking’ on imaging observations being done by ThunderKAT. And it was made through the observation of a single radio pulse or flash. The discovery was not expected. The star concerned is located in a neutron star ‘graveyard’, from which no radio emissions were expected at all.

The two teams worked together to confirm the emissions and determine their origin, establishing the position of the neutron star concerned. This then allowed more sensitive and detailed follow-up observations. The newly discovered neutron star has been designated PSR J0901-4046 and it rotates around its axis once every 76 seconds. Strange as it may seem, a 76-second rotation period is extremely slow for a neutron star.

This rotation speed is more consistent with a white dwarf star, but there are no signs of the multiwavelength emissions characteristic of a white dwarf. Instead, PSR J0901-4046 displays characteristics of pulsars, ultra-long-period magnetars and even fast radio bursts (FRBs). (Pulsars are neutron stars that emit beams of electromagnetic radiation from their magnetic poles; magnetars are neutron stars with extremely powerful magnetic fields; FRBs are incredibly brief and incredibly intense bursts of radio energy, whose origin, or even origins, is/are still far from settled.)

“The radio emission from this neutron star is unlike any we have ever seen before,” highlighted MeerTRAP principal researcher and University of Manchester Professor Ben Stappers. “We get to view it for about 300 milliseconds, which is much longer than for the majority of other radio emitting neutron stars. There seem to be at least seven different pulse types, some of which show strongly periodic structure, which could be interpreted as seismic vibrations of the neutron star. These pulses might be giving us vital insight into the nature of the emission mechanism for these sources.”

“The sensitivity that MeerKAT provides, combined with the sophisticated searching that was possible with MeerTRAP and an ability to make simultaneous images of the sky made this discovery possible,” explained Oxford University (UK) radio astronomer and ThunderKAT team member Dr Ian Heywood. “Even then it took an eagle eye to recognise it for something that was possibly a real source because it was so unusual looking!”