Oscillations and tidal deformations of crystallized white dwarfs

Abstract

Long predicted more than fifty years ago, strong evidence for the existence of crystalline cores inside white dwarfs has recently been obtained by the Gaia space telescope. It is thus important to investigate how a crystalline core may affect the properties and dynamics of white dwarfs. In this paper, we first study the dependence of the frequencies of the fundamental (f), interfacial (i), and shear (s) oscillation modes on the size of the crystalline core. We find that the frequencies of the i- and s-modes depend sensitively on the size of the core, while the frequency of the f-mode is affected only slightly by at most a few percent for our chosen white dwarf models. We next consider the tidal deformability of crystallized white dwarfs and find that the effect of crystallization becomes significant only when the radius of the core is larger than about 70% of the stellar radius. The tidal deformability can change by a few to about 10 percent when a white dwarf becomes fully crystallized. We also show that there exist approximate equation-of-state insensitive relations connecting the mass, moment of inertia, tidal deformability, and f-mode frequency for pure fluid white dwarfs. Depending on the stellar mass and composition, however, these relations can be affected by a few percent when the white dwarf is crystallized. These changes could leave an imprint on the gravitational waves emitted from the late inspiral or merger of white dwarf binaries, which may be detectable by future space-borne gravitational wave detectors.

12 pages, 18 figures, accepted for publication in MNRAS

References in corpus (12)

• Concepts and status of Chinese space gravitational wave detection projects
• The LISA-Taiji network
• Current challenges in the physics of white dwarf stars
• Multipolar universal relations between f-mode frequency and tidal deformability of compact stars
• Surrogate model for an aligned-spin effective one body waveform model of binary neutron star inspirals using Gaussian process regression
• The Physics of Crystallization from Globular Cluster White Dwarf Stars in NGC 6397
• The formation of ultra-massive carbon-oxygen core white dwarfs and their evolutionary and pulsational properties
• Elastic properties of polycrystalline dense matter
• Measuring Individual Masses of Binary White Dwarfs with Space-based Gravitational-wave Interferometers
• Electron exchange and polarization effects on electron captures and neutron emissions by nuclei in white dwarfs and neutron stars
• I-Love-Q Relations for Realistic White Dwarfs
• Neutron star crust in Voigt approximation: general symmetry of the stress-strain tensor and an universal estimate for the effective shear modulus

Cited by in corpus (3)

• Effects of light-mass fermionic dark matter on the equilibrium and stability of white dwarfs
• Ultra low-mass and small-radius white dwarfs made of heavy elements
• Compact dwarfs made of light-quark nuggets