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Nonlinear evolution of the r-modes in neutron stars
L Lindblom1, J E Tohline, M Vallisneri
1Theoretical Astrophysics 130-33, California Institute of Technology, Pasadena, California 91125, USA.
Physical Review Letters
|February 15, 2001
Summary
Neutron-star r-modes destabilized by gravitational radiation cause significant angular momentum and energy loss. Strong shocks rapidly damp these modes, leading to differential rotation in the star.
Area of Science:
- Astrophysics
- Stellar Evolution
- Gravitational Wave Physics
Background:
- Neutron stars possess rapidly rotating cores.
- Gravitational radiation can destabilize neutron-star oscillations (r-modes).
- Understanding r-mode evolution is crucial for neutron-star physics.
Purpose of the Study:
- To investigate the nonlinear evolution of unstable neutron-star r-modes.
- To quantify the energy and angular momentum lost during r-mode damping.
- To analyze the resulting fluid dynamics within the neutron star.
Main Methods:
- Numerical solutions of full nonlinear fluid equations.
- Simulations of r-mode instability driven by gravitational radiation.
- Analysis of shock development and mode damping.
Main Results:
- Dimensionless r-mode amplitude grows to order unity.
- Strong shocks develop, leading to rapid damping of the mode.
- The neutron star loses ~40% angular momentum and ~50% rotational kinetic energy.
- Significant differential rotation develops, concentrated near the surface and poles.
Conclusions:
- Gravitational radiation-driven r-mode instability is a potent damping mechanism.
- The process results in substantial energy and angular momentum dissipation.
- Differential rotation is a key outcome of nonlinear r-mode evolution in neutron stars.