Fundamental Tests of White Dwarf Cooling Physics with Wide Binaries

Abstract

We present follow-up spectroscopy and a detailed model atmosphere analysis of 29 wide double white dwarfs, including eight systems with a crystallized C/O core member. We use state-of-the-art evolutionary models to constrain the physical parameters of each star, including the total age. Assuming that the members of wide binaries are coeval, any age difference between the binary members can be used to test the cooling physics for white dwarf stars, including potential delays due to crystallization and ${}^{22}$Ne distillation. We use our control sample of 14 wide binaries with non-crystallized members to show that this method works well; the control sample shows an age difference of only $\Delta$Age = $-0.03\pm$ 0.15 Gyr between its members. For the eight crystallized C/O core systems we find a cooling anomaly of $\Delta$Age= 1.13${}_{-1.07}^{+1.20}$ Gyr. Even though our results are consistent with a small additional cooling delay ($\sim 1$ Gyr) from ${}^{22}$Ne distillation and other neutron-rich impurities, the large uncertainties make this result not statistically significant. Nevertheless, we rule out cooling delays longer than 3.6 Gyr at the 99.7% ($3\sigma$) confidence level for 0.6-0.9 $M_{\odot }$ white dwarfs. Further progress requires larger samples of wide binaries with crystallized massive white dwarf members. We provide a list of subgiant + white dwarf binaries that could be used for this purpose in the future.

19 pages, including 6 figures and 4 tables, accepted for publication in ApJ

References in corpus (40)

• Gaia Data Release 2. Summary of the contents and survey properties
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• Kinematics of Metal-Poor Stars in the Galaxy. III. Formation of the Stellar Halo and Thick Disk as Revealed from a Large Sample of Non-Kinematically Selected Stars
• Updated Electron-Conduction Opacities: The Impact on Low-Mass Stellar Models
• A million binaries from Gaia eDR3: sample selection and validation of Gaia parallax uncertainties
• A catalogue of white dwarfs in Gaia EDR3
• 3D maps of the local ISM from inversion of individual color excess measurements
• On the Spectral Evolution of Hot White Dwarf Stars. I. A Detailed Model-Atmosphere Analysis of Hot White Dwarfs from SDSS DR12
• The White Dwarf Initial-Final Mass Relation for Progenitor Stars From 0.85 to 7.5 M${}_{\odot }$
• Three-dimensional mapping of the local interstellar medium with composite data
• A white dwarf cooling age of 8 Gyr for NGC 6791 from physical separation processes
• On the Measurement of Fundamental Parameters of White Dwarfs in the Gaia Era
• Core crystallization and pile-up in the cooling sequence of evolving white dwarfs
• The 100 pc White Dwarf Sample in the SDSS Footprint
• A cooling anomaly of high-mass white dwarfs
• Current challenges in the physics of white dwarf stars
• On the evolution of ultra-massive white dwarfs
• Analysis of Helium-Rich White Dwarfs Polluted by Heavy Elements in the Gaia Era
• Gaia DR2 reveals a star formation burst in the disc 2-3 Gyr ago
• White Dwarf Cosmochronology in the Solar Neighborhood
• A New Generation of Cool White Dwarf Atmosphere Models. IV. Revisiting the Spectral Evolution of Cool White Dwarfs
• The initial-final mass relationship from white dwarfs in common proper motion pairs
• ${}^{22}$Ne Phase Separation As A Solution To The Ultramassive White Dwarf Cooling Anomaly
• New Conductive Opacities for White Dwarf Envelopes
• The Physics of Crystallization from Globular Cluster White Dwarf Stars in NGC 6397
• The Canada-France Imaging Survey: Reconstructing the Milky Way Star Formation History from its White Dwarf Population
• Constraints on the Initial-Final Mass Relation from Wide Double White Dwarfs
• Forever young white dwarfs: when stellar ageing stops
• Buoyant crystals halt the cooling of white dwarf stars
• Chasing Lyman alpha-emitting galaxies at z = 8.8
• Constraining the solar neighbourhood age-metallicity relation from white dwarf-main sequence binaries
• Carbon-Oxygen Phase Separation in MESA White Dwarf Models
• Star formation history of the solar neighbourhood as told by Gaia
• Improved Constraints on the Initial-to-Final Mass Relation of White Dwarfs using Wide Binaries
• The Cooling of Massive White Dwarfs from Gaia EDR3
• Phase Separation in Ultramassive White Dwarfs
• Ensemble Properties of the White Dwarf Population of the Old, Solar Metallicity Open Star Cluster Messier 67
• A Crystallizing White Dwarf in a Sirius-Like Quadruple System
• Today a Duo, But Once a Trio? The Double White Dwarf HS 2220$+$2146 May Be A Post-Blue Straggler Binary