Radiation from an off-centred rotating dipole in vacuum

Abstract

When a neutron star forms, after the collapse of its progenitor, a strong magnetic field survives in its interior. This magnetic topology is usually assumed to be well approximated by a dipole located right at the centre of the star. However, there is no particular reason why this dipole should be attached to this very special point. A slight shift from the stellar centre could have strong implications for the surrounding electromagnetic field configuration leading to clear observational signatures. We study the effect of the most general off-centred dipole anchored in the neutron star interior. Exact analytical solutions are given in vacuum outside the star to any order of accuracy in the small parameter $\epsilon =d/R$, where $d$ is the displacement of the dipole from the stellar centre and $R$ the neutron star radius. As a simple diagnostic of this decentred dipole, the spin-down luminosity and the torque exerted on its crust are computed to the lowest leading order in~$\epsilon$. Results are compared to earlier works and a discussion on repercussions on pulsar braking index and multi-wavelength light curves is proposed.

arXiv commentAccepted for publication in MNRAS

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• Joint radio and X-ray modelling of PSR~J1136+1551
• Pulsar gamma-ray emission in the radiation reaction regime
• Multipolar electromagnetic fields around neutron stars: general-relativistic vacuum solutions
• Polarized emission from of an off-centred dipole
• The rocket effect mechanism in neutron stars in supernova remnants
• Apparent dispersion in pulsar braking index measurements caused by timing noise
• Pulsed emission from a rotating off-centred magnetic dipole in vacuum
• Magnetic quadri-dipolar stars rotating in vacuum
• Impact of an off-centred dipole on neutron star binaries
• Off-centred force-free neutron star magnetospheres
• Application of a two dipole model to PSR J1640-4631, a pulsar with an anomalous braking index
• General relativistic calculation of magnetic field and Power loss for a misaligned pulsar
• Memory Effects in Scattering from Accelerating Bodies
• Gamma-radiation sky maps from compact binaries