The internal structure of neutron stars and white dwarfs, and the Jacobi virial equation

Neutron Stars (NSs) are compact stellar objects that are stable solutions in General Relativity. Their internal structure is usually described using an equation of state that involves the presence of ordinary matter and its interactions. However there is now a large consensus that an elusive sector of matter in the universe, described as dark matter, remains as yet undiscovered. In such a case, NSs should contain both, baryonic and dark matter. We argue that depending on the nature of the dark matter and in certain circumstances, the two matter components would form a mixture inside NSs that could trigger further changes, some of them observable. The very existence of NSs constrains the nature and interactions of dark matter in the universe.

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White Dwarf Seismology at the Université de Montréal

International Astronomical Union Colloquium ◽

10.1017/s0252921100117063 ◽

1993 ◽

Vol 139 ◽

pp. 120-120

Author(s):

G. Fontaine ◽

P. Brassard ◽

P. Bergeron ◽

F. Wesemael

Keyword(s):

Specific Heat ◽

Cooling Rate ◽

Internal Structure ◽

White Dwarf ◽

White Dwarfs ◽

Period Change ◽

Core Material ◽

The Core ◽

Core Composition ◽

Chemical Stratification

Over the last several years, we have developed a comprehensive program aimed at better understanding the properties of pulsating DA white dwarfs (or ZZ Ceti stars). These stars are nonradial pulsators of the g-type, and their study can lead to inferences about their internal structure. For instance, the period spectrum of a white dwarf is most sensitive to its vertical chemical stratification, and one of the major goals of white dwarf seismology is to determine the thickness of the hydrogen layer that sits on top of a star. This can be done, in principle, by comparing in detail theoretical period spectra with the periods of the observed excited modes. Likewise, because the cooling rate of a white dwarf is very sensitive to the specific heat of its core material (and hence to its composition), it is possible to infer the core composition through measurements and interpretations of rates of period change in a pulsator.

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Resonance model for high-frequency QPOs in white dwarfs, neutron stars and black holes

New Astronomy Reviews ◽

10.1016/j.newar.2008.03.014 ◽

2008 ◽

Vol 51 (10-12) ◽

pp. 841-845 ◽

Cited By ~ 5

Author(s):

Włodzimierz Kluźniak

Keyword(s):

Black Holes ◽

Neutron Stars ◽

High Frequency ◽

White Dwarfs ◽

Resonance Model

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The internal structure of ZZ Cet stars using quantitative asteroseismology: The case of R548

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313014464 ◽

2013 ◽

Vol 9 (S301) ◽

pp. 285-288

Author(s):

N. Giammichele ◽

G. Fontaine ◽

P. Brassard ◽

S. Charpinet

Keyword(s):

Internal Structure ◽

White Dwarf ◽

White Dwarfs ◽

Optimization Technique ◽

Seismic Model ◽

The Core ◽

Spectroscopic Analyses ◽

Core Composition ◽

Oscillation Modes ◽

Chemical Stratification

AbstractWe explore quantitatively the low but sufficient sensitivity of oscillation modes to probe both the core composition and the details of the chemical stratification of pulsating white dwarfs. Until recently, applications of asteroseismic methods to pulsating white dwarfs have been far and few, and have generally suffered from an insufficient exploration of parameter space. To remedy this situation, we apply to white dwarfs the same double-optimization technique that has been used quite successfully in the context of pulsating hot B subdwarfs. Based on the frequency spectrum of the pulsating white dwarf R548, we are able to unravel in a robust way the unique onion-like stratification and the chemical composition of the star. Independent confirmations from both spectroscopic analyses and detailed evolutionary calculations including diffusion provide crucial consistency checks and add to the credibility of the inferred seismic model. More importantly, these results boost our confidence in the reliability of the forward method for sounding white dwarf internal structure with asteroseismology.

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