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<p>Low-field magnetars have dipolar magnetic fields of 10<sup>12</sup>–10<sup>13</sup> G, 10–100 times weaker than the values of magnetic-field strength <i>B</i> ≈ 10<sup>14</sup>–10<sup>15</sup> G used to define classical magnetars, yet they produce similar X-ray bursts and outbursts. Using direct numerical simulations of magnetothermal 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 a proto-neutron star. We find that these simulations naturally explain key characteristics of low-field magnetars: weak (≲10<sup>13</sup> G) dipolar magnetic fields, strong small-scale fields and magnetically induced crustal failures producing X-ray bursts. These findings suggest that the formation channel of low-<i>B</i> magnetars is distinct from that for classical magnetars, reflecting potential differences in proto-neutron-star dynamos.</p>

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A connection between proto-neutron-star Tayler–Spruit dynamos and low-field magnetars

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年2月4日

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  • Andrei Igoshev,
  • Paul Barrère,
  • Raphaël Raynaud,
  • Jérome Guilet,
  • Toby Wood,
  • Rainer Hollerbach

摘要

Low-field magnetars have dipolar magnetic fields of 1012–1013 G, 10–100 times weaker than the values of magnetic-field strength B ≈ 1014–1015 G used to define classical magnetars, yet they produce similar X-ray bursts and outbursts. Using direct numerical simulations of magnetothermal 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 a proto-neutron star. We find that these simulations naturally explain key characteristics of low-field magnetars: weak (≲1013 G) dipolar magnetic fields, strong small-scale fields and magnetically induced crustal failures producing X-ray bursts. These findings suggest that the formation channel of low-B magnetars is distinct from that for classical magnetars, reflecting potential differences in proto-neutron-star dynamos.