English

From proto-neutron star dynamo to low-field magnetars

High Energy Astrophysical Phenomena 2025-01-10 v1

Abstract

Low-field magnetars have dipolar magnetic fields that are 10-100 times weaker than the threshold, B1014B \gtrsim 10^{14} G, used to define classical magnetars, yet they produce similar X-ray bursts and outbursts. Using the first direct numerical simulations of magneto-thermal evolution starting from a dynamo-generated magnetic field, we show that the low-field magnetars can be produced as a result of a Tayler--Spruit dynamo inside the proto-neutron star. We find that these simulations naturally explain key characteristics of low-field magnetars: (1) weak (1013\lesssim 10^{13} G) dipolar magnetic fields, (2) strong small-scale fields, and (3) magnetically induced crustal failures producing X-ray bursts. These findings suggest two distinct formation channels for classical and low-field magnetars, potentially linked to different dynamo mechanisms.

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Cite

@article{arxiv.2501.04768,
  title  = {From proto-neutron star dynamo to low-field magnetars},
  author = {Andrei Igoshev and Paul Barrère and Raphaël Raynaud and Jérome Guilet and Toby Wood and Rainer Hollerbach},
  journal= {arXiv preprint arXiv:2501.04768},
  year   = {2025}
}

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