The Cooling of Old White Dwarfs in 47 Tucanae

Abstract

We analyse the cooling of white dwarfs in the globular cluster 47 Tucanae (47 Tuc) using deep observations from the Hubble Space Telescope that resolve the white dwarf cooling sequence to late enough cooling times that the envelope has become convectively coupled to the core. At these late times, the thickness of the outer H envelope is an important consideration in modelling the cooling. Using the stellar evolution software Modules for Experiments in Stellar Astrophysics, we create a suite of white dwarf cooling models for different thicknesses of the H envelope and different white dwarf masses. An unbinned likelihood analysis is performed to compare the cooling models to the observations in order to constrain the values of these key parameters. We find that thicker H envelopes are preferred, with the best-fitting models reproducing the observed cumulative 47 Tuc white dwarf luminosity functions well.

arXiv comment23 pages, 13 figures, published in MNRAS

References in corpus (43)

• Modules for Experiments in Stellar Astrophysics (MESA)
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars
• Modules for Experiments in Stellar Astrophysics (MESA): Binaries, Pulsations, and Explosions
• Modules for Experiments in Stellar Astrophysics (MESA): Convective Boundaries, Element Diffusion, and Massive Star Explosions
• Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation
• Gaia Early Data Release 3: Photometric content and validation
• PARSEC evolutionary tracks of massive stars up to $350M_{\odot }$ at metallicities 0.0001$\le Z\le$0.04
• Modules for Experiments in Stellar Astrophysics (MESA): Time-Dependent Convection, Energy Conservation, Automatic Differentiation, and Infrastructure
• Updated Electron-Conduction Opacities: The Impact on Low-Mass Stellar Models
• An Improved Spectroscopic Analysis of DA White Dwarfs from the Sloan Digital Sky Survey Data Release 4
• On the Spectral Evolution of Hot White Dwarf Stars. I. A Detailed Model-Atmosphere Analysis of Hot White Dwarfs from SDSS DR12
• Found: The missing blue opacity in atmosphere models of cool hydrogen white dwarfs
• Synthetic photometry for carbon rich giants, I. Hydrostatic dust-free models
• YBC, a stellar bolometric corrections database with variable extinction coefficients: an application to PARSEC isochrones
• The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters
• Atmospheres from very low-mass stars to extrasolar planets
• An Age Difference of 2 Gyr between a Metal-Rich and a Metal-Poor Globular Cluster
• CN abundance variations on the main sequence of 47 Tuc
• The WISE Extended Source Catalogue (WXSC) I: The 100 Largest Galaxies
• A Dynamical Signature of Multiple Stellar Populations in 47 Tucanae
• A New Generation of Cool White Dwarf Atmosphere Models. I. Theoretical Framework and Applications to DZ Stars
• Synthetic photometry for M and K giants and stellar evolution: hydrostatic dust-free model atmospheres and chemical abundances
• New Conductive Opacities for White Dwarf Envelopes
• New PARSEC database of alpha-enhanced stellar evolutionary tracks and isochrones I. Calibration with 47 Tuc (NGC104) and the improvement on RGB bump
• The Clusters AgeS Experiment (CASE). IV. Analysis of the Eclipsing Binary V69 in the Globular Cluster 47 Tuc
• Ultra-Deep Hubble Space Telescope Imaging of the Small Magellanic Cloud: The Initial Mass Function of Stars with M <~ 1 Msun
• Distances to the globular clusters 47 Tucanae and NGC 362 using Gaia DR2 parallaxes
• Theoretical Uncertainties in Red Giant Branch Evolution: The Red Giant Branch Bump
• The Red-Giant Branch Bump Revisited: Constraints on Envelope Overshooting in a Wide Range of Masses and Metallicities
• A Deep, Wide-Field, and Panchromatic View of 47 Tuc and the SMC with HST: Observations and Data Analysis Methods
• On the red-giant luminosity bump
• On the Delta V_HB_bump parameter in Globular Clusters
• On the magnitude difference between the main sequence turn off and the red giant branch bump in Galactic globular clusters
• Star clusters as laboratories for stellar and dynamical evolution
• Electron conduction opacities at the transition between moderate and strong degeneracy: Uncertainties and impact on stellar models
• Weighing stars: the identification of an Evolved Blue Straggler Star in the globular cluster 47 Tucanae
• Investigating the Consistency of Stellar Evolution Models with Globular Cluster Observations via the Red Giant Branch Bump
• When do stars in 47 Tucanae lose their mass?
• On a new parameter to estimate the helium content in old stellar systems
• Dynamical estimate of post main sequence stellar masses in 47 Tucanae
• Constraining white dwarf structure and neutrino physics in 47 Tucanae
• The Onset of Convective Coupling and Freezing in the White Dwarfs of 47 Tucanae