Speaker
Description
Low-field magnetars have dipolar magnetic fields of $10^{12}$--$10^{13}$ G, 10-100 times weaker than the values of magnetic-field strength $B\approx$ $10^{14}$--$10^{15}$ 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 ($\leq 10^{13}$ G) dipolar magnetic fields, strong small-scale fields and magnetically induced crustal failures producing X-ray bursts. We run new simulations with different stratifications and magnetic Prandtl number as well as volumetric forcing. Some of these new simulations similarly produce low-B magnetars while other produce neutron star with properties similar to central compact objects.