The origin of ultramassive white dwarfs: hints from Gaia EDR3

Abstract

Gaia Data Release 2 revealed a population of ultramassive white dwarfs on the Q branch that are moving anomalously fast for a local disc population with their young photometric ages. As the velocity dispersion of stars in the local disc increases with age, a proposed explanation of these white dwarfs is that they experience a cooling delay that causes current cooling models to infer photometric ages much younger than their true ages. To explore this explanation, we investigate the kinematics of ultramassive white dwarfs within 200 pc of the Sun using the improved Gaia Early Data Release 3 observations. We analyse the transverse motions of 0.95 - 1.25 $M_{\odot }$ white dwarfs, subdivided by mass and age, and determine the distributions of the three-dimensional components of the transverse velocities. The results are compared to expectations based on observed kinematics of local main-sequence stars. We find a population of photometrically young ($\sim$ 0.5 - 1.5 Gyr) ultramassive ($\sim$ 1.15 - 1.25 $M_{\odot }$) white dwarfs for which the transverse velocity component in the direction of Galactic rotation is more dispersed than for local disc stars of any age; thus, it is too dispersed to be explained by any cooling delay in white dwarfs originating from the local disc. Furthermore, the dispersion ratio of the velocity components in the Galactic plane for this population is also inconsistent with a local disc origin. We discuss some possible explanations of this kinematically anomalous population, such as a halo origin or production through dynamical effects of stellar triple systems.

11 pages, 3 figures, published in MNRAS

References in corpus (44)

• The Gaia mission
• New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey
• Southern Massive Stars at High Angular Resolution: Observational Campaign and Companion Detection
• The Geneva-Copenhagen Survey of the Solar neighbourhood II. New uvby calibrations and rediscussion of stellar ages, the G dwarf problem, age-metallicity diagram, and heating mechanisms of the disk
• A Catalog of Multiplicity among Bright Stellar Systems
• A catalogue of white dwarfs in Gaia EDR3
• On the Spectral Evolution of Hot White Dwarf Stars. I. A Detailed Model-Atmosphere Analysis of Hot White Dwarfs from SDSS DR12
• Lidov-Kozai Cycles with Gravitational Radiation: Merging Black Holes in Isolated Triple Systems
• Dynamical age differences among coeval star clusters as revealed by blue stragglers
• Vertical distribution of Galactic disk stars IV - AMR and AVR from clump giants
• The triple evolution dynamical instability: Stellar collisions in the field and the formation of exotic binaries
• Kinematic modelling of the Milky Way using the RAVE and GCS stellar surveys
• Origin and evolution of moving groups I. Characterization in the observational kinematic-age-metallicity space
• Re-visiting the relations: Galactic thin disc age-velocity dispersion relation
• Gaia DR2 reveals a star formation burst in the disc 2-3 Gyr ago
• On the age heterogeneity of the Pleiades, Hyades and Sirius moving groups
• Black hole-neutron star mergers from triples
• The age-velocity dispersion relation of the Galactic discs from LAMOST-Gaia data
• Spin-Orbit Misalignment of Merging Black-Hole Binaries with Tertiary Companions
• ${}^{22}$Ne Phase Separation As A Solution To The Ultramassive White Dwarf Cooling Anomaly
• Stellar triples on the edge; Comprehensive overview of the evolution of destabilised triples leading to stellar and binary exotica
• Induced Ellipticity for Inspiraling Binary Systems
• The formation of ultra-massive carbon-oxygen core white dwarfs and their evolutionary and pulsational properties
• Asteroseismology of ZZ Ceti stars with fully evolutionary white dwarf models: I. The impact of the uncertainties from prior evolution on the period spectrum
• Chaotic dynamics of wide triples induced by galactic tides: a novel channel for producing compact binaries, mergers, and collisions
• Toward Precision Cosmochronology: A New C/O Phase Diagram for White Dwarfs
• The Most Massive White Dwarfs in the Solar Neighborhood
• Search and analysis of blue straggler stars in open clusters
• The Merger Fraction of Ultramassive White Dwarfs
• Reconstructing the Pleiades with Gaia EDR3
• Kinematic properties of white dwarfs. Galactic orbital parameters and age-velocity dispersion relation
• Evolution of massive stellar triples and implications for compact object binary formation
• Local Stellar Kinematics and Oort Constants from the LAMOST A-type Stars
• Return of the TEDI: revisiting the Triple Evolution Dynamical Instability channel in triple stars
• A statistical view on stable and unstable Roche lobe overflow of a tertiary star onto the inner binary in triple systems
• Kinematic structures of the Solar neighbourhood revealed by Gaia DR1/TGAS and RAVE
• The evolution of ultra-massive carbon oxygen white dwarfs
• Cooling Delays from Iron Sedimentation and Iron Inner Cores in White Dwarfs
• The Cooling of Massive White Dwarfs from Gaia EDR3
• Phase Separation in Ultramassive White Dwarfs
• Impact of Convective Boundary Mixing on the TP-AGB
• Formation and Evolution of Blue Stragglers in 47 Tucanae
• The kinematics of Galactic disc white dwarfs in Gaia DR2
• The velocity distribution of white dwarfs in Gaia EDR3

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