http://arxiv.org/abs/2012.06307
In this paper, we attribute high braking indices $n>3$ of two magnetars SGR 0501$+$4516 and 1E 2259$+$586 to the decrease in their inclination angles using the double magnetic-dipole model proposed by Hamil et al.(2016). In this model, there are two magnetic moments inside a neutron star, one is generated by the rotation effect of a charged sphere, $M_{1}$, and the other is generated by the magnetization of ferromagnetically ordered material, $M_{2}$. Our calculations indicate that the magnetic moment $M_{2}$ would evolve towards alignment with the spin axis of the two magnetars, and cause their magnetic inclination angles to decrease. We also define a ratio $\eta=M_{2}/M_{1}$, which reflects the magnetization degree, and find that the values of $\eta$ of the two magnetars are about two-orders of magnitude higher than that of rotationally powered pulsar PSR J1640-4631 with $n=3.15(3)$, assuming that they have the same rate of decrease in their inclination angles.
F. Yan, Z. Gao, W. Yang, et. al.
Mon, 14 Dec 20
50/74
Comments: 6 pages,3 figures,5 tables. arXiv admin note: text overlap with arXiv:1909.01699 by other authors
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