Implications of magnetar non-precession

Abstract

The objects known as anomalous X-ray pulsars and soft gamma repeaters are commonly identified with magnetars, neutron stars with ultrastrong magnetic fields. The rotational history of these objects has, so far, revealed no evidence of free precession. At the same time these objects do not generally appear to have magnetic axes nearly parallel or orthogonal to their spin axes. In this paper we show that the combination of these two observations, together with simple rigid-body dynamics, leads to non-trivial predictions about the interior properties of magnetars: either (i) elastic stresses in magnetar crusts are close to the theoretical upper limit above which the crustal matter yields or (ii) there is a "pinned" superfluid component in the magnetar interior. As a potentially observable consequence of these ideas we point out that, in the case of no pinned superfluidity, magnetars of stronger magnetic field strength than those currently observed would have to be nearly aligned/orthogonal rotators.

5 pages. To appear in MNRAS

References in corpus (6)

• The Breaking Strain of Neutron Star Crust and Gravitational Waves
• Magnetic fields in axisymmetric neutron stars
• Mountains on Neutron Stars: Accreted vs. Non-Accreted crusts
• Relativistic models of magnetars: structure and deformations
• Gravitational wave emission from rotating superfluid neutron stars
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Cited by in corpus (3)

• Possible Evidence for Free Precession of a Strongly Magnetized Neutron Star in the Magnetar 4U 0142+61
• What can PSR J1640-4631 tell us about the internal physics of this neutron star?
• Precession of magnetars: dynamical evolutions and modulations on polarized electromagnetic waves