Non-Linear Development of the Secular Bar-Mode Instability in Rapidly Rotating Neutron Stars
We present results from investigations of the nonlinear development of the secular bar-mode instability that is driven by gravitational radiation-reaction (GRR) forces in rotating neutron stars. Our fully three-dimensional hydrodynamical simulations have shown that, in the absence of any competing v...
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ndltd-LSU-oai-etd.lsu.edu-etd-10282004-1146542013-01-07T22:49:33Z Non-Linear Development of the Secular Bar-Mode Instability in Rapidly Rotating Neutron Stars Ou, Shangli Physics & Astronomy We present results from investigations of the nonlinear development of the secular bar-mode instability that is driven by gravitational radiation-reaction (GRR) forces in rotating neutron stars. Our fully three-dimensional hydrodynamical simulations have shown that, in the absence of any competing viscous effects, initially uniformly rotating axisymmetric n=1/2 polytropic stars with a ratio of rotational to gravitational potential energy greater than the critical limit are driven by GRR forces to a bar-like structure, as predicted by linear theory. The pattern frequency of the bar slows to nearly zero, that is, the bar becomes almost stationary as viewed from an inertial frame of reference as GRR forces remove energy and angular momentum from the star. In this "Dedekind-like" state, rotational energy is stored as motion of the fluid in highly noncircular orbits inside the bar. However, in a very short time after its formation, the bar loses its initially coherent structure as the ordered flow inside the bar is disrupted by what appears to be a purely hydrodynamical, short-wavelength, "shearing" type instability. The gravitational waveforms generated by such an event are determined, and an estimate of the detectability of these waves is presented. Our results also suggest that since a Dedekind-like configuration is susceptible to this turbulent instability, the long believed evolutionary path of a secularly unstable star driven by gravitational radiation toward the Dedekind ellipsoid, becomes questionable. Theda Daniels-Race Luis Lehner Gabriela Gonzalez Juhan Frank Joel E. Tohline LSU 2004-10-29 text application/pdf http://etd.lsu.edu/docs/available/etd-10282004-114654/ http://etd.lsu.edu/docs/available/etd-10282004-114654/ en unrestricted I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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Physics & Astronomy Ou, Shangli Non-Linear Development of the Secular Bar-Mode Instability in Rapidly Rotating Neutron Stars |
description |
We present results from investigations of the nonlinear development of the secular bar-mode instability that is driven by gravitational
radiation-reaction (GRR) forces in rotating neutron stars. Our fully three-dimensional hydrodynamical simulations have shown that, in the absence of any competing viscous effects,
initially uniformly rotating axisymmetric n=1/2 polytropic stars with a ratio of rotational to gravitational potential energy greater than the critical limit are driven by GRR forces to a bar-like structure, as predicted by linear theory. The pattern frequency of the bar slows to nearly zero, that is, the bar becomes almost stationary as viewed from an inertial frame of reference as GRR forces remove energy and angular momentum from the star. In this "Dedekind-like" state, rotational energy is stored as motion of the fluid in highly noncircular orbits inside the bar. However, in a very short time after its formation, the bar loses its initially coherent structure as the ordered flow inside the bar is disrupted by what appears to be a purely hydrodynamical, short-wavelength, "shearing" type instability. The gravitational waveforms generated by such an
event are determined, and an estimate of the detectability of these waves is presented. Our results also suggest that since a Dedekind-like configuration is susceptible to this turbulent
instability, the long believed evolutionary path of a secularly unstable star driven by gravitational radiation toward the Dedekind ellipsoid, becomes questionable. |
author2 |
Theda Daniels-Race |
author_facet |
Theda Daniels-Race Ou, Shangli |
author |
Ou, Shangli |
author_sort |
Ou, Shangli |
title |
Non-Linear Development of the Secular Bar-Mode Instability in Rapidly Rotating Neutron Stars |
title_short |
Non-Linear Development of the Secular Bar-Mode Instability in Rapidly Rotating Neutron Stars |
title_full |
Non-Linear Development of the Secular Bar-Mode Instability in Rapidly Rotating Neutron Stars |
title_fullStr |
Non-Linear Development of the Secular Bar-Mode Instability in Rapidly Rotating Neutron Stars |
title_full_unstemmed |
Non-Linear Development of the Secular Bar-Mode Instability in Rapidly Rotating Neutron Stars |
title_sort |
non-linear development of the secular bar-mode instability in rapidly rotating neutron stars |
publisher |
LSU |
publishDate |
2004 |
url |
http://etd.lsu.edu/docs/available/etd-10282004-114654/ |
work_keys_str_mv |
AT oushangli nonlineardevelopmentofthesecularbarmodeinstabilityinrapidlyrotatingneutronstars |
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1716477071200354304 |