Open AccessBurial of the polar magnetic field of an accreting neutron star – I. Self‐consistent analytic and numerical equilibria
Author(s) -
Payne D. J. B.,
Melatos A.
Publication year - 2004
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.07798.x
Subject(s) - physics , neutron star , polar , dipole , astrophysics , accretion (finance) , magnetic dipole , stellar magnetic field , magnetic field , pulsar , radius , magnetic flux , magnetic moment , flux (metallurgy) , magnetohydrodynamics , condensed matter physics , astronomy , coronal mass ejection , quantum mechanics , materials science , computer security , solar wind , computer science , metallurgy
The hydromagnetic structure of a neutron star accreting symmetrically at both magnetic poles is calculated as a function of accreted mass, M a , and polar cap radius, starting from a centred magnetic dipole and evolving through a quasi‐static sequence of two‐dimensional, Grad–Shafranov equilibria. The calculation is the first to track fully the growth of high‐order magnetic multipoles, due to equatorward hydromagnetic spreading, while simultaneously preserving flux‐freezing and a self‐consistent mass–flux distribution. Equilibria are constructed numerically by an iterative scheme and analytically by Green functions. Two key results are obtained, with implications for recycled pulsars. (i) The mass required to reduce significantly the magnetic dipole moment, 10 −5 M ⊙ , greatly exceeds previous estimates (∼10 −10 M ⊙ ) , which ignored the confining stress exerted by the compressed equatorial magnetic field. (ii) Magnetic bubbles, disconnected from the stellar surface, form in the later stages of accretion ( M a ≳ 10 −4 M ⊙ ) .