Low-field magnetars formation

Led by scientists from Newcastle University, University of Leeds and France, the paper was published in the journal Nature Astronomy. The researchers identified the Tayler-Spruit dynamo caused by fall back of supernova material as mechanism leading to formation of low-field magnetars. This new work solves the mystery of low-field magnetars formation puzzling scientists since low-field magnetar discovery in 2010.

The team used advanced numerical simulations to model the magneto-thermal evolution of these stars, finding that a specific dynamo process within the proto-neutron star can generate these weaker magnetic fields.

Investigating complicated magnetic fields of neutron stars.

Study lead author, Dr Andrei Igoshev, Research Fellow at Newcastle University’s School of Mathematics, Statistics and Physics, said: “Neutron stars are born in supernova explosions. Most of external layers of massive star are removed during the supernova, but some material falls back making the neutron star to spin faster. Researchers show that this process plays a very important role for formation of magnetic field via the Tayler-Spruit dynamo mechanism. This mechanism was suggested theoretically nearly a quarter of century ago, but it was only recently reproduced using computer simulations. The magnetic field formed via this mechanism is very complicated with internal field inside the start which is much stronger than the external.”

Magnetars are known to have enormous magnetic fields which are hundreds trillions times stronger the Earth magnetic fields. Due to these fields magnetars are bright and variable sources of X-ray radiation. Some of less magnetised stars also have similar X-ray emission. These less magnetised stars are known as low-field magnetars. Dynamo is a mechanism which convert plasma motion into magnetic fields.

Dr Igoshev is establishing a new research group at Newcastle University to further investigate complicated magnetic fields of neutron stars.

Reference:

Igoshev, A., Barrère, P., Raynaud, R. et al. A connection between proto-neutron-star Tayler–Spruit dynamos and low-field magnetars. Nat Astron (2025). https://doi.org/10.1038/s41550-025-02477-y