2022ApJ...938...91K -
Astrophys. J., 938, 91 (2022/October-3)
Accumulation of Elastic Strain toward Crustal Fracture in Magnetized Neutron Stars.
KOJIMA Y.
Abstract (from CDS):
This study investigates elastic deformation driven by the Hall drift in a magnetized neutron-star crust. Although the dynamic equilibrium initially holds without elastic displacement, the magnetic-field evolution changes the Lorentz force over a secular timescale, which inevitably causes the elastic deformation to settle in a new force balance. Accordingly, elastic energy is accumulated, and the crust is eventually fractured beyond a particular threshold. We assume that the magnetic field is axially symmetric, and we explicitly calculate the breakup time, maximum elastic energy stored in the crust, and spatial shear-stress distribution. For the barotropic equilibrium of a poloidal dipole field expelled from the interior core without a toroidal field, the breakup time corresponds to a few years for the magnetars with a magnetic-field strength of ∼1015 G; however, it exceeds 1 Myr for normal radio pulsars. The elastic energy stored in the crust before the fracture ranges from 1041 to 1045 erg, depending on the spatial-energy distribution. Generally, a large amount of energy is deposited in a deep crust. The energy released at a fracture is typically ∼1041 erg when the rearrangement of elastic displacements occurs only in the fragile shallow crust. The amount of energy is comparable to the outburst energy on the magnetars.
Abstract Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.
Journal keyword(s):
Neutron stars - Magnetars - Compact objects - High energy astrophysics - Magnetic fields - Soft gamma-ray repeaters
Simbad objects:
2
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