2002/06/30 by Curt Cutler · 6 citations
Earth and Planetary Sciences · Engineering · Physics and Astronomy · #Geophysics and Sensor Technology #High-pressure geophysics and materials #Pulsars and Gravitational Waves Research #astro-ph #gr-qc
paper · pdf · doi:10.1103/physrevd.66.084025
published as Phys.Rev. D66 (2002) 084025 · 7 pages; submitted to PRD; only minor revisions
arxiv created 2002/08/23 · openalex publication_date 2002/10/30 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We show that NS's with large toroidal B fields tend naturally to evolve into potent gravitational-wave (GW) emitters. The toroidal field Bt tends to distort the NS into a prolate shape, and this magnetic distortion dominates over the oblateness ``frozen into'' the NS crust for Bt\ensuremath\gtrsim3.4\ifmmode×\else\texttimes\fi1012G(\ensuremathνs/300Hz)2. An elastic NS with frozen-in B field of this magnitude is clearly secularly unstable: the wobble angle between the NS's angular momentum Ji and the star's magnetic axis nBi grows on a dissipation time scale until Ji and nBi are orthogonal. This final orientation is clearly the optimal one for GW emission. The basic cause of the instability is quite general, so we conjecture that the same final state is reached for a realistic NS, with superfluid core. Assuming this, we show that for LMXB's with Bt\ensuremath∼2\ifmmode×\else\texttimes\fi1012\ensuremath-2\ifmmode×\else\texttimes\fi1014G, the spindown from GW's is sufficient to balance the accretion torque---supporting a suggestion by Bildsten. The spindown rates of most millisecond pulsars can also be attributed to GW emission sourced by toroidal B fields, and both these sources could be observed by LIGO II. While the first-year spindown of a newborn NS is most likely dominated by electromagnetic processes, reasonable values of Bt and the (external) dipolar field Bd can lead to detectable levels of GW emission, for a newborn NS in our own Galaxy.