Evolution of the Magnetic Field of a Neutron Star During Polar-Cap Accretion

Abstract

Neutron stars that have experienced episodes of mass transfer exhibit lower magnetic dipole moments μ than other neutron stars, e.g. binary radio pulsars with high-mass (μ ∼ 1028G cm3) and low-mass (μ ∼ 1027G cm3) companions, isolated millisecond pulsars (μ ∼ 1026G cm3), and accreting objects in low-mass X-ray binaries (μ < 1027G cm3). Indeed, the μ-versus-orbital-period and μ-versus-age relations for low-mass and high-mass binaries imply that μ decreases monotonically with accreted mass Ma (Taam & van den Heuvel 1986; van den Heuvel & Bitzaraki 1995). Simple Ohmic field decay cannot be responsible given the existence of cold and therefore old white-dwarf companions (Kulkarni 1986). Alternat..