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 {\it 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 $1.369M_{\odot }$ 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 in the Newtonian computations, with relative differences of up to $\sim 50$ \% for the highest-mass models ($1.369M_{\odot }$) 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 $\sim 1.29M_{\odot }$ cannot be ignored in the asteroseismological analysis of ultra-massive ZZ Ceti stars.

15 pages, 21 figures, 2 tables. Accepted for publication in MNRAS

References in corpus (25)

• The K2 Mission: Characterization and Early results
• Pulsating White Dwarf Stars and Precision Asteroseismology
• A catalogue of white dwarfs in Gaia EDR3
• The 100 pc White Dwarf Sample in the SDSS Footprint
• A highly magnetised and rapidly rotating white dwarf as small as the Moon
• Asteroseismic inferences on GW Vir variable stars in the frame of new PG 1159 evolutionary models
• Measurements of Physical Parameters of White Dwarfs: A Test of the Mass-Radius Relation
• An ultra-massive white dwarf with a mixed hydrogen-carbon atmosphere as a likely merger remnant
• Non-radial Oscillation Modes of Compact Stars with a Crust
• The formation of ultra-massive carbon-oxygen core white dwarfs and their evolutionary and pulsational properties
• The Most Massive White Dwarfs in the Solar Neighborhood
• Discovery of 74 new bright ZZ Ceti stars in the first three years of TESS
• The Merger Fraction of Ultramassive White Dwarfs
• Searching for ZZ Ceti White Dwarfs in the Gaia Survey
• Detections and Constraints on White Dwarf Variability from Time-Series GALEX Observations
• A population synthesis fitting of the $Gaia$ resolved white dwarf binary population within 100 pc
• The evolution of ultra-massive carbon oxygen white dwarfs
• Structure and evolution of ultra-massive white dwarfs in general relativity
• On Trapped Modes In Variable White Dwarfs As Probes Of The ${}^{12}$C($\alpha ,\gamma$)${}^{16}$O Reaction Rate
• WD J004917.14$-$252556.81, the Most Massive Pulsating White Dwarf
• Carbon-oxygen ultra-massive white dwarfs in general relativity
• R-mode oscillations in accreting white dwarfs in cataclysmic variables
• Gravity modes on rapidly rotating accreting white dwarfs and their variation after dwarf novae
• Newtonian pulsations of relativistic ONe-core ultra-massive DA white dwarfs
• Relativistic Corrections in White Dwarf Asteroseismology

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