2002/11/14 by Thomas W. Baumgarte, Stuart L. Shapiro · 3 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Black hole (networking) #Electromagnetic field #General relativity #Gravitation #Gravitational collapse #Magnetic dipole #Magnetic field #Pulsars and Gravitational Waves Research #Relativity and Gravitational Theory #Rotating black hole #Spin-flip #Stellar black hole #astro-ph #gr-qc
paper · pdf · doi:10.1086/346104
published as Astrophys.J.585:930-947,2003 · 22 pages, 12 figures; scheduled for March 10 issue of ApJ
arxiv created 2002/11/14 · openalex publication_date 2003/03/10 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We study of the collapse of a magnetized spherical star to a black hole in general relativity theory. The matter and gravitational fields are described by the exact Oppenheimer-Snyder solution for the collapse of a spherical, homogeneous dust ball. We adopt a "dynamical Cowling approximation," whereby the matter and the geometry (metric), while highly dynamical, are unaffected by the electromagnetic fields. The matter is assumed to be perfectly conducting and threaded by a dipole magnetic field at the onset of collapse. We determine the subsequent evolution of the magnetic and electric fields without approximation; the fields are determined analytically in the matter interior and numerically in the vacuum exterior. We apply junction conditions to match the electromagnetic fields across the stellar surface. We use this model to experiment with several coordinate gauge choices for handling spacetime evolution characterized by the formation of a black hole and the associated appearance of singularities. These choices range from "singularity-avoiding" time coordinates to "horizon-penetrating" time coordinates accompanied by black hole excision. The later choice enables us to integrate the electromagnetic fields arbitrarily far into the future. At late times the longitudinal magnetic field in the exterior has been transformed into a transverse electromagnetic wave; part of the electromagnetic radiation is captured by the hole and the rest propagates outward to large distances. The solution we present for our simple scenario can be used to test codes designed to treat more general evolutions of relativistic magnetohydrodynamics fluids flowing in strong gravitational fields in dynamical spacetimes.