Reaching the End of the White Dwarf Cooling Sequence in NGC 6791

Abstract

We present new observations of the white dwarf sequence of the old open cluster NGC 6791. The brighter peak previously observed in the white dwarf luminosity function (WDLF) is now better delineated, and the second, fainter peak that we suggested earlier is now confirmed. A careful study suggests that we have reached the end of the white dwarf sequence. The WDs that create the two peaks in the WDLF show a significant turn to the blue in the color-magnitude diagram. The discrepancy between the age from the WDs and that from the main sequence turnoff remains, and we have an additional puzzle in the second peak in the WDLF. Canonical WD models seem to fail --at least at ~25%-level-- in reproducing the age of clusters of this metallicity. We discuss briefly possible ways of arriving at a theoretical understanding of the WDLF.

arXiv comment29 pages, 10 figures (4 in low resolution), 1 table. Accepted (2007 December 19) on ApJ

References in corpus (27)

• On the variation of the Initial Mass Function
• A large stellar evolution database for population synthesis studies. I. Scaled solar models and isochrones
• The Photometric Performance and Calibration of the HST Advanced Camera For Surveys
• The Hubble Ultra Deep Field
• Drizzle: A Method for the Linear Reconstruction of Undersampled Images
• The Initial-Final Mass Relation: Direct Constraints at the Low Mass End
• A consistent explanation for ${}^{12}$C/${}^{13}$C, ${}^7$Li, and ${}^3$He anomalies in red giant stars
• The cooling of CO white dwarfs: influence of the internal chemical distribution
• Transforming observational data and theoretical isochrones into the ACS/WFC Vega-mag system
• The white dwarf cooling sequence in NGC 6791
• NGC 6791: an exotic open cluster or the nucleus of a tidally disrupted galaxy?
• The ages of very cool hydrogen-rich white dwarfs
• Pure hydrogen atmosphere for very cool white dwarfs
• Stellar Evolution in NGC 6791: Mass Loss on the Red Giant Branch and the Formation of Low Mass White Dwarfs
• The open cluster initial-final mass relationship and the high-mass tail of the white dwarf distribution
• Evolution and colours of helium-core white dwarf stars: the case of low metallicity progenitors
• The metallicity of the old open cluster NGC 6791
• Gravitational Settling of ^{22}Ne in Liquid White Dwarf Interiors--Cooling and Seismological Effects
• The energetics of crystallizing white dwarfs revisited again
• High resolution infrared spectroscopy of the old open cluster NGC6791
• Evolutionary calculations of phase separation in crystallizing white dwarf stars
• Color--Magnitude Diagrams and Luminosity Functions down to the Hydrogen Burning Limit. III. A Preliminary HST Study of NGC6791
• Isochrones and Luminosity Functions for Old White Dwarfs
• Gravitational settling of 22Ne and white dwarf evolution
• A Search for Planets in the Old Open Cluster NGC 6791
• The absolute motion of the peculiar cluster NGC6791
• White Dwarfs in NGC 6791: Avoiding the Helium Flash

Cited by in corpus (75)

• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. I. Overview of the Project and Detection of Multiple Stellar Populations
• Evolutionary and pulsational properties of white dwarf stars
• Hot subluminous stars
• Asteroseismology of old open clusters with Kepler: direct estimate of the integrated RGB mass loss in NGC6791 and NGC6819
• A white dwarf cooling age of 8 Gyr for NGC 6791 from physical separation processes
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters - XVII. Public Catalogue Release
• Age and helium content of the open cluster NGC 6791 from multiple eclipsing binary members. II. age dependencies and new insights
• A large stellar evolution database for population synthesis studies: VI. White dwarf cooling sequences
• The HST large programme on $\omega$ Centauri - II. internal kinematics
• The End of the White Dwarf Cooling Sequence in M4: an efficient approach
• Comparison of theoretical white dwarf cooling timescales
• Age and helium content of the open cluster NGC 6791 from multiple eclipsing binary members. I. Measurements, methods, and first results
• Hubble Space Telescope Proper motion (HSTPROMO) Catalogs of Galactic Globular Clusters. VI. Improved data reduction and internal-kinematic analysis of NGC 362
• The BaSTI Stellar Evolution Database: models for extremely metal-poor and super-metal-rich stellar populations
• A new standard: Age and distance for the open cluster NGC 6791 from the eclipsing binary member V20
• Sodium and Oxygen Abundances in the Open Cluster NGC 6791 from APOGEE H-Band Spectroscopy
• The Puzzling White Dwarf Cooling Sequence in NGC6791: A Simple Solution
• Evolution of white dwarf stars with high-metallicity progenitors: the role of 22Ne diffusion
• Asteroseismic inferences on red giants in open clusters NGC 6791, NGC 6819 and NGC 6811 using Kepler
• Hubble Space Telescope survey of Magellanic Cloud star clusters. Photometry and astrometry of 113 clusters and early results
• Multi-Gigayear White Dwarf Cooling Delays from Clustering-Enhanced Gravitational Sedimentation
• The updated BaSTI stellar evolution models and isochrones. III. White Dwarfs
• An upper limit to the secular variation of the gravitational constant from white dwarf stars
• The M4 Core Project with HST -- II. Multiple Stellar Populations at the Bottom of the Main Sequence
• The end of the white dwarf cooling sequence in M 67
• Pulsations in Hydrogen Burning Low Mass Helium White Dwarfs
• Evolution and colors of helium-core white dwarf stars with high-metallicity progenitors
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XVIII. Proper-motion kinematics of multiple stellar populations in the core regions of NGC 6352
• The HST Large Programme on NGC6752. II. Multiple populations at the bottom of the main sequence probed in NIR
• Very low mass white dwarfs with a C-O core
• Carbon-Oxygen Phase Separation in MESA White Dwarf Models
• The bottom of the white dwarf cooling sequence in the old open cluster NGC 2158
• A Double White-Dwarf Cooling Sequence in ω Centauri
• The White Dwarf Age of NGC 2477
• WIYN Open Cluster Study. XXXIX. Abundances in NGC 6253 from HYDRA Spectroscopy of the Li 6708 A Region
• A comparative analysis of the observed white dwarf cooling sequence from globular clusters
• The Helium Abundance of NGC 6791 from Modeling of Stellar Oscillations
• The white dwarf population of NGC 6397
• White dwarfs as Physics laboratories: lights and shadows
• JWST-TST Proper Motions: I. High-Precision NIRISS Calibration and Large Magellanic Cloud Kinematics
• Stellar graveyards: Clustering of compact objects in globular clusters NGC 3201 and NGC 6397
• Asteroseismic Study on Cluster Distance Moduli for RGB Stars in NGC 6791 and NGC 6819
• The white dwarf cooling sequence of 47 Tucanae
• 2D kinematics of massive stars near the Galactic Center
• Survey of multiple populations in globular clusters among very low-mass stars
• Hubble Space Telescope observations of the Kepler-field cluster NGC 6819. I. The bottom of the white dwarf cooling sequence
• Hubble Space Telescope analysis of stellar populations within the globular cluster G1 (Mayall II) in M31
• The HST large programme on omega Centauri -- IV. catalogue of two external fields
• The HST large programme on $\omega$ Centauri -- V. Exploring the Ultracool Dwarf Population with Stellar Atmosphere and Evolutionary Modelling
• Star formation history of resolved galaxies. I. The Method
• Ensemble Properties of the White Dwarf Population of the Old, Solar Metallicity Open Star Cluster Messier 67
• oMEGACat II -- Photometry and proper motions for 1.4 million stars in Omega Centauri and its rotation in the plane of the sky
• The white dwarf cooling sequence of NGC 6791: a unique tool for stellar evolution
• Star Cluster Ages in the Gaia Era
• The HST Large Programme on NGC 6752. III. Detection of the Peak of the White Dwarf Luminosity Function
• The effects of ${}^{22}$Ne sedimentation and metallicity on the local 40 pc white dwarf luminosity function
• The HST large programme on NGC 6752 -- IV. The White Dwarf Sequence
• Asteroseismology of Pulsating Stars
• A Turnoff Detached Binary Star V568 Lyr in the Kepler Field of the Oldest Open Cluster (NGC 6791) in the Galaxy
• The Absolute Magnitudes of Red Horizontal Branch Stars in the ugriz System
• Blue Stragglers as tracers of the dynamical state of two clusters in the Small Magellanic Cloud: NGC 339 and NGC 419
• Revisiting the luminosity function of single halo white dwarfs
• Ne22 distillation and the cooling sequence of the old metal-rich open cluster NGC 6791
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XIII. ACS/WFC Parallel-Field Catalogues
• Faint Stars in a Faint Galaxy: II. The Low Mass Stellar Initial Mass Function of the Boötes I Ultrafaint Dwarf Spheroidal Galaxy
• Faint Stars in a Faint Galaxy: I. Ultra Deep Photometry of the Boötes I Ultra Faint Dwarf Galaxy
• Kinematic complexity around NGC419: resolving the proper motion of the cluster, the Small Magellanic Cloud and the Magellanic Bridge
• White Dwarfs in Globular Clusters
• Pulsations of the Low Mass ZZ Ceti Star HS 1824+6000
• The Next Generation Virgo Cluster Survey. XXVIII. Characterization of the Galactic White Dwarf Population
• Open clusters: probes of galaxy evolution and bench tests of stellar models
• A Massive and Eccentric Binary Millisecond Pulsar in the Globular Cluster M10
• Evidence for Dynamical Filtering: High Binary Fraction, Hard-binary Excess, and Unresolved Triples in the Surviving Core of NGC 6791
• JWST observations of 47 Tucanae: I. The low-mass main sequence down to the hydrogen-burning limit
• The mass functions of multiple stellar populations in 47 Tucanae