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A new class of g-modes in neutron stars

Reisenegger, Andreas and Goldreich, Peter (1992) A new class of g-modes in neutron stars. Astrophysical Journal, 395 (1). pp. 240-249. ISSN 0004-637X. doi:10.1086/171645.

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Because a neutron star is born hot, its internal composition is close to chemical equilibrium. In the fluid core, this implies that the ratio of the number densities of charged particles (protons and electrons) to neutrons, x ≡ n_c/n_n, is an increasing function of the mass density. This composition gradient stably stratifies the matter giving rise to a Brunt-Väisälä frequency N ~ (xg/2H)^(1/2) ~ 500 s^(-1), where g is the gravitational acceleration, and H is the density scale height. Consequently, a neutron star core provides a cavity that supports gravity modes (g-modes). These g-modes are distinct from those previously identified with the thermal stratification of the surface layers and the chemical stratification of the crust. We compute the lowest-order, quadrupolar, g-modes for cold, Newtonian, neutron star models with M/M_☉ = 0.581 and M/M_☉ = 1.405 and show that the crustal and core g-modes have similar periods. We also discuss damping mechanisms and estimate damping rates for the core g-modes. Particular attention is paid to damping due to the emission of gravitational radiation.

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Additional Information:© 1992 American Astronomical Society. Received 1991 September 23; accepted 1992 February 14. We are indebted to a number of colleagues for assistance with this project. The computer code we used to calculate g-modes is a modified version of a code Pawan Kumar wrote to calculate solar p-modes. Curt Cutler provided two relativistic neutron star models, on which preliminary calculations were carried out, and the table from which we constructed the equation of state. He also pointed us to Mendell's work on damping of oscillations in superfluid stars. Norman Murray offered help with the computations. Patrick N. McDermott gave valuable criticisms on a previous version of this paper, and motivated us to numerically evaluate the gravitational wave damping of the g-modes. Finally, our research was supported by NSF grant AST 89-13664, and by NASA grants NAGW 1303 and NAGW 2372.
Group:UNSPECIFIED, Division of Geological and Planetary Sciences
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NSFAST 89-13664
Subject Keywords:stars: neutron, stars: oscillations
Issue or Number:1
Record Number:CaltechAUTHORS:20130313-154510940
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Official Citation:A new class of g-modes in neutron stars Reisenegger, Andreas; Goldreich, Peter Astrophysical Journal, Part 1, vol. 395, no. 1, p. 240-249.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37511
Deposited By: Ruth Sustaita
Deposited On:14 Mar 2013 15:45
Last Modified:09 Nov 2021 23:29

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