Testing White Dwarf Crystallization Theory with Asteroseismology of the Massive Pulsating DA Star BPM 37093

Abstract

It was predicted more than 40 years ago that the cores of the coolest white dwarf stars should eventually crystallize. This effect is one of the largest sources of uncertainty in white dwarf cooling models, which are now routinely used to estimate the ages of stellar populations in both the Galactic disk and the halo. We are attempting to minimize this source of uncertainty by calibrating the models, using observations of pulsating white dwarfs. In a typical mass white dwarf model, crystallization does not begin until the surface temperature reaches 6000-8000 K. In more massive white dwarf models the effect begins at higher surface temperatures, where pulsations are observed in the ZZ Ceti (DAV) stars. We use the observed pulsation periods of BPM 37093, the most massive DAV white dwarf presently known, to probe the interior and determine the size of the crystallized core empirically. Our initial exploration of the models strongly suggests the presence of a solid core containing about 90% of the stellar mass, which is consistent with our theoretical expectations.

minor changes for length, accepted for ApJ Letters

References in corpus (5)

• On the Purity of the ZZ Ceti Instability Strip: Discovery of More Pulsating DA White Dwarfs on the Basis of Optical Spectroscopy
• New evolutionary models for massive ZZ Ceti stars: I. First results for their pulsational properties
• Stellar Structure Modeling using a Parallel Genetic Algorithm for Objective Global Optimization
• White Dwarf Asteroseismology and the ^12C(alpha,gamma)^16O Rate
• Probing the core and envelope structure of DBV white dwarfs

Cited by in corpus (42)

• Automated supervised classification of variable stars I. Methodology
• Pulsating white dwarfs: new insights
• Toward ensemble asteroseismology of ZZ Ceti stars with fully evolutionary models
• On the evolution of ultra-massive white dwarfs
• A Stellar Model-fitting Pipeline for Asteroseismic Data from the Kepler Mission
• Habitable Planets Around White and Brown Dwarfs: The Perils of a Cooling Primary
• New chemical profiles for the asteroseismology of ZZ Ceti stars
• Whole Earth Telescope observations of BPM 37093: a seismological test of crystallization theory in white dwarfs
• The Physics of Crystallization from Globular Cluster White Dwarf Stars in NGC 6397
• Post-main sequence evolution of A star debris discs
• Asteroseismological study of massive ZZ Ceti stars with fully evolutionary models
• Seismological studies of ZZ Ceti stars. I. The model grid and the application to individual stars
• Re-defining the Empirical ZZ Ceti Instability Strip
• Discovery of an ultramassive pulsating white dwarf
• An Isolated White Dwarf with a 70 second Spin Period
• Asteroseismology of ZZ Ceti stars with fully evolutionary white dwarf models: I. The impact of the uncertainties from prior evolution on the period spectrum
• Coulomb crystals in the magnetic field
• Four New Massive Pulsating White Dwarfs Including an Ultramassive DAV
• Discovery of fourteen new ZZ Cetis with SOAR
• New evolutionary models for massive ZZ Ceti stars. II. The effects of crystallization on their pulsational properties
• A 1.05 $M_{\odot }$ Companion to PSR J2222-0137: The Coolest Known White Dwarf?
• Infrared Absorption Investigations Confirm the Extraterrestrial Origin of Carbonado-Diamonds
• Pulsation properties of ultra-massive DA white dwarf stars with ONe cores
• A Dark Spot on a Massive White Dwarf
• Asteroseismology
• Stellar model fits and inversions
• Whole Earth Telescope observations of the hot helium atmosphere pulsating white dwarf EC 20058-5234
• Probing the structure of Kepler ZZ Ceti stars with full evolutionary models-based asteroseismology
• Revisiting axion-electron bremsstrahlung emission rates in astrophysical environments
• Asteroseismological analysis of the ultra-massive ZZ Ceti stars BPM~37093, GD~518, and SDSS~J0840+5222
• A Bayesian Approach to Deriving Ages of Individual Field White Dwarfs
• Cooling Delays from Iron Sedimentation and Iron Inner Cores in White Dwarfs
• Asteroseismology of ZZ Ceti stars with full evolutionary white dwarf models. II. The impact of AGB thermal pulses on the asteroseismic inferences of ZZ Ceti stars
• WD J004917.14$-$252556.81, the Most Massive Pulsating White Dwarf
• Asteroseismology of Pulsating Stars
• The pulsating DA white dwarf star EC 14012-1446: results from four epochs of time-resolved photometry
• Pulsating H-deficient WDs and pre-WDs observed with TESS: V. Discovery of two new DBV pulsators, WD J152738.4-450207.4 and WD 1708-871, and asteroseismology of the already known DBV stars PG 1351+489, EC 20058-5234, and EC 04207-4748
• Seismological challenges for stellar structure
• Seismology and diffusion of ultramassive white dwarf magnetic fields
• Seismic test of the mass-radius relationship of hydrogen-atmospheric white dwarf stars
• Lessons for Asteroseismology from White Dwarf Stars
• The Onset of Convective Coupling and Freezing in the White Dwarfs of 47 Tucanae