Astronomers observe magnetar J1818 that is exhibiting very unusual activity

J1818 was emitting unusual pulsar-like radio waves in May but by June, it had started flickering between magnetar and pulsar-like properties.


Astronomers have seen some bizarre behaviour from a magnetar which is a type of neutron star that is considered to be one of the strongest magnets in the universe. The recent findings throw light on their magnetic property and hence will help scientists understand their creation better. A team from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) and CSIRO conducted the observation and the study was published in the journal Monthly Notices of the Royal Astronomical Society on Monday, 1 February.

 Astronomers observe magnetar J1818 that is exhibiting very unusual activity

Artist’s impression of the active magnetar Swift J1818.0-1607. Credit: Carl Knox, OzGrav.

A magnetized neutron star or magnetars are a very rare cosmic body that has complex and strong magnetic fields. Till date, only 30 or so magnetars have been detected by astronomers in and around the Milky Way. Some of them are capable of emitting radio waves, which is characteristic of a pulsar.

A pulsar the less-magnetic cousins of magnetars that produce beams of radio waves from their magnetic poles.

One such radio pulse emitting magnetar, called Swift J1818.0-1607 or J1818, was discovered in March of 2020. Scientists noticed that it was a radio-loud magnetar, which means a star capable of originating radio pulses. However, the ‘appearance’ of the radio pulses recorded from J1818 were “quite different” from those detected from other such magnetars in the past, read a statement by the ARC Centre of Excellence for Gravitational Wave Discovery.

While radio pulses from magnetars usually maintain a “consistent brightness across a wide range of observing frequencies”, the pulses detected from J1818 were “much brighter at low frequencies than high frequencies”. Scientists were quick to notice that this characteristic was also seen in pulsars. Then the team observed the neutron star for a period of five months in 2020.

Interestingly, J1818 was emitting unusual pulsar-like radio waves in May but by June, it had started flickering between magnetar and pulsar-like properties. This flickering reached its zenith in July before settling into its magnetar-like state thereafter.

Lead author and Swinburne University/ CSIRO PhD student Marcus Lower said they found that the “magnetic axis of J1818 isn't aligned with its rotation axis”, making it the first magnetar with a “misaligned magnetic pole”.

Recently, the Chandra X-Ray Observatory captured an image of a supernova -  RCW 103 - whose centre (1E 1613 ) is made up a neutron star but have recently discovered to actually be a magnetar.


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