A Wolf-Rayet star will likely morph into a magnetic monster

Magnetars are the most magnetic objects in the known universe and we know surprisingly little about their origins and formation.
Chris Young
An artist’s impression of the binary system HD 45166.
An artist’s impression of the binary system HD 45166.

Fabian Bodensteiner 

A team of astronomers carried out observations of a hot, helium-rich Wolf-Rayet star that forms part of a binary system known as HD 45166, a press statement reveals.

They also performed computer simulations and found that the Wolf-Rayet star will likely produce a magnetar when it explodes as a supernova.

The findings shed new light on the formation of magnetars, the most magnetic objects in the universe.

Analyzing a Wolf-Rayet star

Wolf-Rayet stars are some of the most massive, luminous stars in the universe. They are at an advanced stage of stellar evolution, and, as such, they are expelling their outer layers prior to going supernova in a massive cosmic explosion.

They are essentially the exposed helium core of a massive star that has lost its outer hydrogen layers. In March this year, NASA shared a stunning image of a Wolf-Rayet star called WR 124 and its surrounding nebula.

The team of researchers, who published their findings in a paper in the journal Science, observed HD 45166, a binary system with a main sequence star and a hot Wolf-Rayet star companion.

They analyzed new spectropolarimetric observations of HD45166 taken by the Canada-France-Hawaii Telescope as well as archival spectra from other instruments. By investigating these observations, they found that the Wolf-Rayet star has the equivalent of two solar masses and a high magnetic field of 43 kilogauss.

The scientists behind the new study then ran stellar evolution simulations using advanced computer models. The models, which incorporated the new observation data, showed that the Wolf-Rayet star would eventually collapse into a neutron star.

Supernovae may amplify magnetic fields in massive stellar cores

What's more, the team calculated that magnetic flux conservation during the star's core collapse would increase the strength of the star's magnetic field to a range that would see it categorized as a magnetar.

"Our observations and stellar-evolution models therefore indicate that the Wolf-Rayet component could be an immediate progenitor of a magnetar," the authors wrote.

A magnetar is a type of neutron star with an incredibly powerful magnetic field, making it the most powerful type of magnetic object in the known universe.

The origins and formation process of magnetars remain somewhat of a mystery, though. One hypothesis suggests that a supernova explosion can lead to the amplification of a magnetic field in the massive core of the parent star, producing a magnetar.

Though the new findings don't confirm this hypothesis, they add another piece to the magnetar puzzle. With astronomers having recently identified 19 new Wolf-Rayet stars in our nearest galactic neighbor, the Andromeda galaxy, the global astronomical community continues to uncover the mysteries of these highly-luminous stars.

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