General relativistic pulsations of ultra-massive ZZ Ceti stars

Alejandro H. Córsico; S. Reece Boston; Leandro G. Althaus; Mukremin Kilic; S. O. Kepler; María E. Camisassa; Santiago Torres

doi:10.1093/mnras/stad2248

General relativistic pulsations of ultra-massive ZZ Ceti stars

Alejandro H. Córsico, S. Reece Boston, Leandro G. Althaus, Mukremin Kilic, S. O. Kepler, María E. Camisassa, Santiago Torres

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Abstract

Ultra-massive white dwarf stars are currently being discovered at a considerable rate, thanks to surveys such as the Gaia space mission. These dense and compact stellar remnants likely play a major role in Type Ia supernova explosions. It is possible to probe the interiors of ultra-massive white dwarfs through asteroseismology. In the case of the most massive white dwarfs, general relativity could affect their structure and pulsations substantially. In this work, we present results of relativistic pulsation calculations employing relativistic ultra-massive ONe-core white dwarf models with hydrogen-rich atmospheres and masses ranging from 1.29 to with the aim of assessing the impact of general relativity on the adiabatic gravity (g)-mode period spectrum of very high mass ZZ Ceti stars. Employing the relativistic Cowling approximation for the pulsation analysis, we find that the critical buoyancy (Brunt-Väisälä) and acoustic (Lamb) frequencies are larger for the relativistic case, compared to the Newtonian case, due to the relativistic white dwarf models having smaller radii and higher gravities for a fixed stellar mass. In addition, the g-mode periods are shorter in the relativistic case than those in the Newtonian computations, with relative differences of up to ∼ per cent for the highest mass models () and for effective temperatures typical of the ZZ Ceti instability strip. Hence, the effects of general relativity on the structure, evolution, and pulsations of white dwarfs with masses larger than ∼ cannot be ignored in the asteroseismological analysis of ultra-massive ZZ Ceti stars.

Original language	English
Pages (from-to)	5929-5943
Number of pages	15
Journal	Monthly Notices of the Royal Astronomical Society
Volume	524
Issue number	4
DOIs	https://doi.org/10.1093/mnras/stad2248
State	Published - Oct 2023

Funding

We wish to thank the suggestions and comments of an anonymous referee that improved the original version of this work. Part of this work was supported by AGENCIA through the Programa de Modernización Tecnológica BID 1728/OC-AR, by the PIP 112-200801-00940 grant from CONICET, by the National Science Foundation under grants AST-2205736 and PHY-2110335, by the National Aeronautics and Space Administration under grant 80NSSC22K0479, and by the US DOE under contract DE-AC05-00OR22725. ST acknowledges support from MINECO under the PID2020-117252GB-I00 grant and by the AGAUR/Generalitat de Catalunya grant SGR-386/2021. MEC acknowledges grant RYC2021-032721-I, funded by MCIN/AEI/10.13039/501100011033 and by the European Union NextGenerationEU/PRTR. This research has made use of NASA Astrophysics Data System.

Funders	Funder number
AGENCIA	PIP 112-200801-00940
European Union NextGenerationEU/PRTR
National Science Foundation	PHY-2110335, AST-2205736
U.S. Department of Energy	DE-AC05-00OR22725
National Aeronautics and Space Administration	80NSSC22K0479
Generalitat de Catalunya	MCIN/AEI/10.13039/501100011033, SGR-386/2021, RYC2021-032721-I
Consejo Nacional de Investigaciones Científicas y Técnicas
Agència de Gestió d'Ajuts Universitaris i de Recerca
Ministerio de Economía y Competitividad	PID2020-117252GB-I00

Keywords

asteroseismology
relativistic processes
stars: evolution
stars: interiors
stars: oscillations
white dwarfs

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10.1093/mnras/stad2248

Cite this

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title = "General relativistic pulsations of ultra-massive ZZ Ceti stars",

abstract = "Ultra-massive white dwarf stars are currently being discovered at a considerable rate, thanks to surveys such as the Gaia space mission. These dense and compact stellar remnants likely play a major role in Type Ia supernova explosions. It is possible to probe the interiors of ultra-massive white dwarfs through asteroseismology. In the case of the most massive white dwarfs, general relativity could affect their structure and pulsations substantially. In this work, we present results of relativistic pulsation calculations employing relativistic ultra-massive ONe-core white dwarf models with hydrogen-rich atmospheres and masses ranging from 1.29 to with the aim of assessing the impact of general relativity on the adiabatic gravity (g)-mode period spectrum of very high mass ZZ Ceti stars. Employing the relativistic Cowling approximation for the pulsation analysis, we find that the critical buoyancy (Brunt-V{\"a}is{\"a}l{\"a}) and acoustic (Lamb) frequencies are larger for the relativistic case, compared to the Newtonian case, due to the relativistic white dwarf models having smaller radii and higher gravities for a fixed stellar mass. In addition, the g-mode periods are shorter in the relativistic case than those in the Newtonian computations, with relative differences of up to ∼ per cent for the highest mass models () and for effective temperatures typical of the ZZ Ceti instability strip. Hence, the effects of general relativity on the structure, evolution, and pulsations of white dwarfs with masses larger than ∼ cannot be ignored in the asteroseismological analysis of ultra-massive ZZ Ceti stars.",

keywords = "asteroseismology, relativistic processes, stars: evolution, stars: interiors, stars: oscillations, white dwarfs",

author = "C{\'o}rsico, {Alejandro H.} and Boston, {S. Reece} and Althaus, {Leandro G.} and Mukremin Kilic and Kepler, {S. O.} and Camisassa, {Mar{\'i}a E.} and Santiago Torres",

note = "Publisher Copyright: {\textcopyright} 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.",

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AU - Córsico, Alejandro H.

AU - Boston, S. Reece

AU - Althaus, Leandro G.

AU - Kilic, Mukremin

AU - Kepler, S. O.

AU - Camisassa, María E.

AU - Torres, Santiago

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AB - Ultra-massive white dwarf stars are currently being discovered at a considerable rate, thanks to surveys such as the Gaia space mission. These dense and compact stellar remnants likely play a major role in Type Ia supernova explosions. It is possible to probe the interiors of ultra-massive white dwarfs through asteroseismology. In the case of the most massive white dwarfs, general relativity could affect their structure and pulsations substantially. In this work, we present results of relativistic pulsation calculations employing relativistic ultra-massive ONe-core white dwarf models with hydrogen-rich atmospheres and masses ranging from 1.29 to with the aim of assessing the impact of general relativity on the adiabatic gravity (g)-mode period spectrum of very high mass ZZ Ceti stars. Employing the relativistic Cowling approximation for the pulsation analysis, we find that the critical buoyancy (Brunt-Väisälä) and acoustic (Lamb) frequencies are larger for the relativistic case, compared to the Newtonian case, due to the relativistic white dwarf models having smaller radii and higher gravities for a fixed stellar mass. In addition, the g-mode periods are shorter in the relativistic case than those in the Newtonian computations, with relative differences of up to ∼ per cent for the highest mass models () and for effective temperatures typical of the ZZ Ceti instability strip. Hence, the effects of general relativity on the structure, evolution, and pulsations of white dwarfs with masses larger than ∼ cannot be ignored in the asteroseismological analysis of ultra-massive ZZ Ceti stars.

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General relativistic pulsations of ultra-massive ZZ Ceti stars

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