The r-modes of slowly rotating, stratified neutron stars
The r-modes of slowly rotating, stratified neutron stars
The only r-modes that exist in a globally barotropic, rotating, Newtonian star are the fundamental l = |m| solutions, where l and m are the indices of the spherical harmonic Y
l
m that describe the mode’s angular dependence. This is in stark contrast to a stellar model that is non-barotropic throughout its interior, which hosts all the l ≥ |m| perturbations including radial overtones. In reality, neutron stars are stratified with locally barotropic regions. Therefore, we explore how stratification alters a star’s ability to support r-modes. We consider the globally stratified case and examine the behaviour of the modes as the star gets close to barotropicity. In this limit, we find that all but the fundamental l = |m| perturbations change character and become generic inertial modes. Restricting the analysis to l = |m| perturbations, we develop the r-mode equations in order to consider stellar models that exhibit local barotropicity. Our results for such models show that the r-mode overtones diverge and join the inertial modes. In order to see which r-modes persist and retain their character in realistic neutron stars, these calculations will need to be brought into full general relativity.
equation of state, instabilities, stars: neutron, stars: oscillations, stars: rotation
3043-3057
Gittins, Fabian
657ec875-fac3-4606-9dcd-591ef22fc9f6
Andersson, Nils
2dd6d1ee-cefd-478a-b1ac-e6feedafe304
22 March 2023
Gittins, Fabian
657ec875-fac3-4606-9dcd-591ef22fc9f6
Andersson, Nils
2dd6d1ee-cefd-478a-b1ac-e6feedafe304
Gittins, Fabian and Andersson, Nils
(2023)
The r-modes of slowly rotating, stratified neutron stars.
Monthly Notices of the Royal Astronomical Society, 521 (2), .
(doi:10.1093/mnras/stad672).
Abstract
The only r-modes that exist in a globally barotropic, rotating, Newtonian star are the fundamental l = |m| solutions, where l and m are the indices of the spherical harmonic Y
l
m that describe the mode’s angular dependence. This is in stark contrast to a stellar model that is non-barotropic throughout its interior, which hosts all the l ≥ |m| perturbations including radial overtones. In reality, neutron stars are stratified with locally barotropic regions. Therefore, we explore how stratification alters a star’s ability to support r-modes. We consider the globally stratified case and examine the behaviour of the modes as the star gets close to barotropicity. In this limit, we find that all but the fundamental l = |m| perturbations change character and become generic inertial modes. Restricting the analysis to l = |m| perturbations, we develop the r-mode equations in order to consider stellar models that exhibit local barotropicity. Our results for such models show that the r-mode overtones diverge and join the inertial modes. In order to see which r-modes persist and retain their character in realistic neutron stars, these calculations will need to be brought into full general relativity.
Text
2212.04892
- Accepted Manuscript
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stad672
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Accepted/In Press date: 28 February 2023
e-pub ahead of print date: 2 March 2023
Published date: 22 March 2023
Additional Information:
Funding Information:
The authors are grateful for support from STFC via grant number ST/V000551/1. The contribution of FG was partly carried out at the Institute for Nuclear Theory at the University of Washington during the ‘Neutron Rich Matter on Heaven and Earth’ workshop, which is supported by the U.S. Department of Energy grant DE-FG02-00ER41132. The contribution of NA was partly carried out at the Aspen Center for Physics, which is supported by National Science Foundation grant PHY-1607611. He also thanks the Simons Foundation for generous travel support.
Keywords:
equation of state, instabilities, stars: neutron, stars: oscillations, stars: rotation
Identifiers
Local EPrints ID: 482005
URI: http://eprints.soton.ac.uk/id/eprint/482005
ISSN: 1365-2966
PURE UUID: 125f6d74-8370-4516-8181-f8e701cfae7e
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Date deposited: 15 Sep 2023 16:31
Last modified: 18 Mar 2024 04:04
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Author:
Fabian Gittins
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