2012/07/31 by J. Frieben, Joachim Frieben, Luciano Rezzolla +1 · 4 citations
Earth and Planetary Sciences · Physics and Astronomy · #Astrophysics #Classical mechanics #Distortion (music) #Field (mathematics) #Gamma-ray bursts and supernovae #Geometry #High-pressure geophysics and materials #Magnetic field #Neutron star #Physics #Pulsars and Gravitational Waves Research #Quadrupole #Quantum electrodynamics #Quantum mechanics #Rotation (mathematics) #astro-ph.SR #gr-qc
paper · pdf · doi:10.1111/j.1365-2966.2012.22027.x
published as Mon. Not. R. Astron. Soc. 427, 3406-3426 (2012) · Published version with additional correction of remaining typos
openalex publication_date 2012/12/21 · arxiv created 2014/02/13 · arxiv updated 2014/02/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We have computed models of rotating relativistic stars with a toroidal magnetic field and investigated the combined effects of magnetic field and rotation on the apparent shape (i.e. the surface deformation), which could be relevant for the electromagnetic emission, and on the internal matter distribution (i.e. the quadrupole distortion), which could be relevant for the emission of gravitational waves. Using a sample of eight different cold nuclear physics equations of state, we have computed models of maximum field strength, as well as the distortion coefficients for the surface and the quadrupolar deformations. Surprisingly, we find that non-rotating models admit arbitrary levels of magnetization, accompanied by a growth of size and quadrupole distortion to which we could not find a limit. Rotating models, on the other hand, are subject to a mass-shedding limit at frequencies well below the corresponding ones for unmagnetized stars. Overall, the space of solutions can be split into three distinct classes for which the surface deformation and the quadrupole distortion are either prolate and prolate, oblate and prolate, or oblate and oblate, respectively. We also derive a simple formula expressing the relativistic distortion coefficients, which allows one to compute the surface deformation and the quadrupole distortion up to significant levels of rotation and magnetization, essentially covering all known magnetars. Such a formula replaces Newtonian equivalent expressions that overestimate the magnetic quadrupole distortion by about a factor of 6 and are inadequate for strongly relativistic objects like neutron stars.