Constraining the magnetic field geometry of the millisecond pulsar PSR J0030+0451 from joint radio, thermal X-ray, and<i>γ</i>-ray emission
J. Pétri, Sébastien Guillot, L. Guillemot, I. Cognard, G. Theureau, J.‐M. Grießmeier, L. Bondonneau, D. González-Caniulef, N. A. Webb, F. Jankowski, І. P. Kravtsov, James W. McKee, T. D. Carozzi, Baptiste Cecconi, M. Serylak, P. Zarka
Abstract
Context. With the advent of multi-wavelength electromagnetic observations of neutron stars – spanning many decades in photon energies – from radio wavelengths up to X-rays and γ -rays, it has become possible to significantly constrain the geometry and the location of the associated emission regions. Aims. In this work, we use results from the modelling of thermal X-ray observations of PSR J0030+0451 from the Neutron Star Interior Composition Explorer (NICER) mission and phase-aligned radio and γ -ray pulse profiles to constrain the geometry of an off-centred dipole that is able to reproduce the light curves in these respective bands simultaneously. Methods. To this aim, we deduced a configuration with a simple dipole off-centred from the location of the centre of the thermal X-ray hot spots. We show that the geometry is compatible with independent constraints from radio and γ -ray pulsations only, leading to a fixed magnetic obliquity of α ≈ 75° and a line-of-sight inclination angle of ζ ≈ 54°. Results. We demonstrate that an off-centred dipole cannot be rejected by accounting for the thermal X-ray pulse profiles. Moreover, the crescent shape of one spot is interpreted as the consequence of a small-scale surface dipole on top of the large-scale off-centred dipole.