The artist’s impression of the pulsar from the 76th year (in the magenta) compared to other faster rotating sources. Credit: Danielle Futselaar
An international team of astronomers has discovered a strange radio-emitting neutron star that rotates extremely slowly, making one rotation every 76 seconds.
The research team says this is an unusual discovery, as it is located in the cemetery of neutron stars, where they do not expect to see any radio broadcast at all. The discovery was made using the MeerKAT radio telescope in South Africa and published in the journal Natural astronomy on May 30, 2022. The study was led by members of the ERC-funded MeerTRAP (More Transients and Pulsars) group at the University of Manchester.
The source was originally detected by a single flash or pulse from the MeerTRAP tool while monitoring images led by a different team, ThunderKAT. MeerTRAP and ThunderKAT then worked closely together to unravel its origins. By combining data from the two teams, it was possible to confirm the pulsations and obtain an accurate position for the source, allowing detailed and more sensitive follow-up observations.
Neutron stars are extremely dense remnants of a supernova explosion on a massive star. They can produce rays from radio waves that travel around the sky as the neutron star rotates, producing regular lightning bolts like space lights. Scientists currently know about 3,000 of them in our own Milky Way galaxy. However, the new discovery does not look like anything seen so far. The team believes it may belong to the theorized class of ultra-long magnetars with extremely strong magnetic fields.
MeerKAT South African Telescope. Credit: South African Radio Astronomical Observatory (SARAO)
Dr Manisha Caleb, formerly of the University of Manchester and now of the University of Sydney, who led the study, said: “It is amazing that we find radio broadcast from this source for only 0.5% of its rotation period. This means that it is very accidental for the radio beam to intersect with the Earth. Therefore, there are likely to be many more of these very slow-spinning sources in the Galaxy, which has important implications for how neutron stars are born and age.
“Most pulsar studies do not look for such long periods, so we have no idea how many of these sources there may be. In this case, the source was bright enough for us to detect single pulses with the MeerTRAP tool in MeerKAT.
“It is amazing that we detect radio broadcast from this source for only 0.5% of the rotation period. This means that it is very accidental for the radio beam to intersect with the Earth. Therefore, there are likely to be many more of these very slow-spinning sources in the Galaxy, which has important implications for how neutron stars are born and age.
– Dr. Manisha Caleb
The newly discovered neutron star is called PSR J0901-4046 and shows characteristics of pulsars, (ultra long period) magnets and even fast radio bursts. While the produced radio energy assumes a pulsar origin, the pulses with chaotic subpulse components and the polarization of the pulses are reminiscent of magnetars.
While the period of rotation of PSR J0901-4046 may be more compatible with the white dwarf, another less extreme type of stellar remnant, scientists see no support for many waves of this. It is not clear at this time how long this source has been broadcasting on the radio. It was found in a well-studied part of the galaxy, but radio studies usually do not look for such long periods or pulses that last more than a few tens of milliseconds.
Dr. Manisha Caleb. Credit: University of Sydney
“The radio emission from this neutron star is different from what we’ve seen before,” said Professor Ben Stappers of the University of Manchester and lead researcher on the MeerTRAP project. “We can see it in about 300 milliseconds, which is much longer than most other neutron stars. There appear to be at least 7 different types of pulses, some of which show a highly periodic structure that can be interpreted as seismic vibrations of the neutron star. These impulses can give us a vital idea of the nature of the emission mechanism for these sources. “
“The sensitivity that MeerKAT provides, combined with the complex search that was possible with MeerTRAP, and the ability to take simultaneous images of the sky, made this discovery possible. Even then, it took an eagle’s eye to recognize it as something that was probably the real source because it looked so unusual! ” said Dr Ian Haywood of the ThunderKAT team and the University of Oxford, which is collaborating on the study.
Discovering such sources is a challenge to observe, suggesting that there may be a larger undiscovered population waiting to be discovered. This new discovery adds to the possibility of a new class of radio transients, ultra-long neutron stars, suggesting a possible link to the evolution of highly magnetized neutron stars, ultra-long magnets and fast radio bursts.
Reference: “Discovery of a radio-emitting neutron star with an ultra-long rotation period of 76 s” by Manisha Caleb, Ian Haywood, Kaustub Rajwade, Mateusz Malenta, Benjamin Willem Stappers, Ewan Bar, Weiwei Chen, Vincent Vanbore Morelo, Sotiri Einden Day, Michael Kramer, David Buckley, Jaco Brink, Sarah Eliza Motta, Patrick Wade, Patrick Veltevrede, Fabian Jankowski, Mayures Surnis, Sarah Buchner, Mehil Christian Besuidenhout, Laura Nicole Drissien and May Fender: May 20, 2022. / s41550-022-01688-x
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