Hydromagnetic Structure of a Neutron Star Accreting at Its Polar Caps

Publications of the Astronomical Society of Australia

A. Melatos¹ 

[1] E. S. Phinney

关键词: accretion;    accretion disks;    pulsars:;    general;    stars: magnetic fields;    stars: neutron;   

DOI  :  10.1071/AS01056

学科分类：天文学(综合)

来源: CSIRO

【 摘 要 】

The hydromagnetic structure of a neutron star accreting symmetrically at both magnetic poles is calculated as a function of accreted mass, Ma, starting from a polytropic sphere plus central magnetic dipole (Ma =0) and evolving the configuration through a quasistatic sequence of twodimensional, Grad–Shafranov equilibria as Ma increases. It is found that the accreted material spreads equatorward under its own weight, compressing the magnetic field into a thin boundary layer and burying it everywhere except in a narrow, equatorial belt. The magnetic dipole moment of the star is given by µ=5.2×1024(B0/1012.5G)1.3(Ma/10−8Mʘ yr−1)0.18(Ma/Mʘ)−1.3Gcm3, and the fractional difference between its principal moments of inertia is given by Є=2.1×10−5(B0/1012.5G)0.27(Ma/10−8Myr−1)0.18(Ma/Mʘ)1.7, for Ma in the range 10−5Ma/Mʘ10−1,where B0 is the pre-accretion magnetic field strength, and Ma is the accretion rate.

【 授权许可】

Unknown