Model Atmosphere Analysis of Two Very Cool White Dwarfs

Abstract

A detailed analysis of the very cool white dwarfs SDSS 1337+00 and LHS 3250 is presented. Model atmosphere calculations with improved collision-induced absorptions by molecular hydrogen indicate that a pure hydrogen composition can be ruled out, and that the strong infrared absorption observed in these cool stars is better explained in terms of collisions of H2 with neutral helium. It is shown that even though the overall shape of the observed energy distributions can be reproduced reasonably well with helium-rich models, the peak of the energy distribution near 6000 A is always predicted too narrow. The extreme helium-rich composition inferred for both objects is discussed in the broader context of the extremely cool white dwarfs reported in various surveys.

Accepted for publication in the Astrophysical Journal; 14 pages 9 figures

Cited by in corpus (56)

• Found: The missing blue opacity in atmosphere models of cool hydrogen white dwarfs
• A Catalog of Spectroscopically Identified White Dwarf Stars in the First Data Release of the Sloan Digital Sky Survey
• The White Dwarf Luminosity Function from SDSS Imaging Data
• The White Dwarf Cooling Sequence of NGC6397
• On the Measurement of Fundamental Parameters of White Dwarfs in the Gaia Era
• The 100 pc White Dwarf Sample in the SDSS Footprint
• Current challenges in the physics of white dwarf stars
• On type Ia supernovae and the formation of single low-mass white dwarfs
• Cool White Dwarfs in the Sloan Digital Sky Survey
• A New Generation of Cool White Dwarf Atmosphere Models. IV. Revisiting the Spectral Evolution of Cool White Dwarfs
• Calculated spectra for HeH+ and its effect on the opacity of cool metal poor stars
• Rosseland and Planck mean opacities for primordial matter
• Discovery of New Ultracool White Dwarfs in the Sloan Digital Sky Survey
• A Detailed Model Atmosphere Analysis of Cool White Dwarfs in the Sloan Digital Sky Survey
• On the Interpretation of High Velocity White Dwarfs as Members of the Galactic Halo
• The Solar Neighborhood. XIX. Discovery and Characterization of 33 New Nearby White Dwarf Systems
• An accurate mass and radius measurement for an ultracool white dwarf
• Cool White Dwarfs Revisited -- New Spectroscopy and Photometry
• A 1.05 $M_{\odot }$ Companion to PSR J2222-0137: The Coolest Known White Dwarf?
• The Solar Neighborhood XXXI: Discovery of an Unusual Red+White Dwarf Binary at ~25 Parsecs via Astrometry and UV Imaging
• Spectral analysis of ultra-cool white dwarfs polluted by planetary debris
• Ultracool white dwarfs and the age of the Galactic disc
• The role of HeH+ in cool helium rich white dwarfs
• Additional Ultracool White Dwarfs Found in the Sloan Digital Sky Survey
• New UltraCool and Halo White Dwarf Candidates in SDSS Stripe 82
• Infrared Photometric Analysis of White Dwarfs from The Two Micron All Sky Survey and the Spitzer Space Telescope
• On the Nature of Ultracool White Dwarfs: Not so Cool Afterall
• On the Dissociation Equilibrium of H2 in Very Cool, Helium-Rich White Dwarf Atmospheres
• Spitzer Observations of the Oldest White Dwarfs in the Solar Neighborhood
• Visitors from the Halo: 11 Gyr old White Dwarfs in the Solar Neighborhood
• A Nearby Old Halo White Dwarf Candidate from the Sloan Digital Sky Survey
• The Mystery Deepens: Spitzer Observations of Cool White Dwarfs
• A New Method for Finding Nearby White Dwarf Exoplanets and Detecting Biosignatures
• A Critical Examination of Halo White Dwarf Candidates
• Pressure Distortion of the H${}_2$-He Collision-Induced Absorption at the Photosphere of Cool White Dwarf Stars
• The ultra-cool white dwarf companion of PSR J0751+1807
• Distant White Dwarfs in the US Naval Observatory Flagstaff Station Parallax Sample
• Trigonometric parallaxes of high velocity halo white dwarf candidates
• Discovery of an Ultracool White Dwarf Companion
• Infrared absorption of dense helium and its importance in the atmospheres of cool white dwarfs
• Mid-Infrared High-Contrast Imaging of HD 114174 B : An Apparent Age Discrepancy in a "Sirius-Like" Binary System
• Theoretical study of the line profiles of the hydrogen perturbed by collisions with protons
• Near-UV absorption in very cool DA white dwarfs
• Component masses of young, wide, non-magnetic white dwarf binaries in the SDSS DR7
• Photometric Identification of Cool White Dwarfs
• Photometric constraints on white dwarfs and the identification of extreme objects
• The brightest pure-H ultracool white dwarf
• New Halo White Dwarf Candidates in the Sloan Digital Sky Survey
• White dwarf -- red giant star binaries as Type Ia supernova progenitors: with and without magnetic confinement
• Cool White Dwarfs Identified in the Second Data Release of the UKIRT Infrared Deep Sky Survey
• Cool Versus Ultracool White Dwarfs
• A New Ultracool White Dwarf Discovered in the SuperCOSMOS Sky Survey
• White dwarfs with hydrogen-deficient atmospheres and the dark matter content of the Galaxy
• An ultra-cool white dwarf serendipitously found with COMBO-17
• A new statistical mechanical formalism for gases
• The Luminosity Function for White Dwarfs in the SuperCOSMOS Sky Survey