Phd records
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A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenWed, 31 Jan 2024 19:22:34 +0000Dynamical Stability of Nascent Neutron Stars
https://resolver.caltech.edu/CaltechTHESIS:03112014-101628149
Authors: {'items': [{'email': 'ytliu@illinois.edu', 'id': 'Liu-Yuk-Tung', 'name': {'family': 'Liu', 'given': 'Yuk Tung'}, 'show_email': 'NO'}]}
Year: 2003
DOI: 10.7907/61ZS-XQ28
<p>This thesis presents a study of the dynamical stability of nascent neutron stars resulting from the
accretion induced collapse of rapidly rotating white dwarfs.</p>
<p>Chapter 2 and part of Chapter 3 study the equilibrium models for these neutron stars. They are
constructed by assuming that the neutron stars have the same masses, angular momenta, and specific
angular momentum distributions as the pre-collapse white dwarfs. If the pre-collapse white dwarf is
rapidly rotating, the collapsed object will contain a high density central core of size about 20 km,
surrounded by a massive accretion torus extending to hundreds of kilometers from the rotation axis.
The ratio of the rotational kinetic energy to gravitational binding energy, β, of these neutron stars
is all found to be less than 0.27.</p>
<p>Chapter 3 studies the dynamical stability of these neutron stars by numerically evolving the
linearized hydrodynamical equations. A dynamical bar-mode instability is observed when the β of
the star is greater than the critical value β<sub>d</sub> ≈ 0.25. It is expected that the unstable mode will
persist until a substantial amount of angular momentum is carried away by gravitational radiation.
The detectability of these sources is studied and it is estimated that LIGO II is unlikely to detect
them unless the event rate is greater than 10<sup>-6</sup>/year/galaxy.</p>
<p>All the calculations on the structure and stability of the neutron stars in Chapters 2 and 3
are carried out using Newtonian hydrodynamics and gravity. Chapter 4 studies the relativistic
effects on the structure of these neutron stars. New techniques are developed and used to construct
neutron star models to the first post-Newtonian (1PN) order. The structures of the 1PN models
are qualitatively similar to the corresponding Newtonian models, but the values of β are somewhat
smaller. The maximum β for these 1PN neutron stars is found to be 0.24, which is 8% smaller than
the Newtonian result (0.26). However, relativistic effects will also change the critical value β<sub>d</sub>. A
detailed post-Newtonian stability analysis has yet to be carried out to study the relativistic effects
on the dynamical stability of these neutron stars.</p>https://thesis.library.caltech.edu/id/eprint/8122