Radio-emitting neutron stars are objects with spin periods ranging from milliseconds to tens of seconds; as they age and spin more slowly, their radio emission is expected to cease. However, astronomers from the University of Sydney and elsewhere have discovered an ultra-long-period radio-emitting neutron star, PSR J0901-4046, with spin properties distinct from the known neutron stars. With a spin period of about 76 seconds, an age of 5.3 million years and a narrow pulse duty cycle, it is uncertain how PSR J0901-4046’s radio emission is generated and challenges our current understanding of how these systems evolve.
MeerKAT image of the PSR J0901-4046 region at 1.28 GHz. Image credit: Caleb et al., doi: 10.1038/s41550-022-01688-x.
Neutron stars are extremely dense remnants of supernova explosions of massive stars.
There are about 3,000 neutron stars known in our Milky Way Galaxy. However, PSR J0901-4046 is unlike anything seen so far.
It could belong to the theorized class of ultra-long-period magnetars — stars with extremely strong magnetic fields.
PSR J0901-4046 was initially detected from a single pulse on September 27, 2020.
It was then possible to confirm multiple pulses using simultaneous consecutive eight-second-long images of the sky, to confirm its position.
The neutron star is nearly 5.3 million years old and rotates extremely slowly, completing one rotation every 75.88 seconds.
The discovery was made by the MeerTRAP team using the MeerKAT radio telescope in South Africa.
“Amazingly we only detect radio emission from this source for 0.5% of its rotation period,” said Dr. Manisha Caleb, an astronomer at the University of Sydney.
“This means that it is very lucky that the radio beam intersected with the Earth.”
“It is therefore likely that there are many more of these very slowly spinning stars in the Galaxy, which has important implications for understanding how neutron stars are born and age.”
“The majority of pulsar surveys do not search for periods this long, so we have no idea how many of these stars might exist.”
According to the team, PSR J0901-4046 has at least seven different pulse types, some of which occur at regular intervals.
It shows characteristics of pulsars, ultra-long-period-magnetars and even fast radio bursts — brief flashes of radio emission in random locations in the sky.
“This is the beginning of a new class of neutron stars,” Dr. Caleb said.
“How or whether it relates to other classes is yet to be explored. There are likely many more out there. We need only look!”
The discovery is reported in a paper in the journal Nature Astronomy.
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M. Caleb et al. Discovery of a radio-emitting neutron star with an ultra-long spin period of 76 s. Nat Astron, published online May 30, 2022; doi: 10.1038/s41550-022-01688-x
Source link: https://www.sci.news/astronomy/ultra-long-period-magnetar-10859.html
