Additional Ultracool White Dwarfs Found in the Sloan Digital Sky Survey

Abstract

We identify seven new ultracool white dwarfs discovered in the Sloan Digital Sky Survey (SDSS). The SDSS photometry, spectra, and proper motions are presented, and additional BVRI data are given for these and other previously discovered ultracool white dwarfs. The observed colors span a remarkably wide range, qualitatively similar to colors predicted by models for very cool white dwarfs. One of the new stars (SDSS J1251+44) exhibits strong collision-induced absorption (CIA) in its spectra, while the spectra and colors of the other six are consistent with mild CIA. Another of the new discoveries (SDSS J2239+00A) is part of a binary system -- its companion is also a cool white dwarf, and other data indicate that the companion exhibits an infrared flux deficiency, making this the first binary system composed of two CIA white dwarfs. A third discovery (SDSS J0310-00) has weak Balmer emission lines. The proper motions of all seven stars are consistent with membership in the disk or thick disk.

Accepted for Astrophysical Journal. 16 pages (includes 3 figures)

References in corpus (34)

• The Sloan Digital Sky Survey: Technical Summary
• The 2.5 m Telescope of the Sloan Digital Sky Survey
• The USNO-B Catalog
• The Sloan Digital Sky Survey Photometric Camera
• The u'g'r'i'z' Standard Star Network
• The Sixth Data Release of the Sloan Digital Sky Survey
• Spectroscopic Target Selection in the Sloan Digital Sky Survey: The Quasar Sample
• Astrometric Calibration of the Sloan Digital Sky Survey
• A photometricity and extinction monitor at the Apache Point Observatory
• Astrometry and Photometry for Cool Dwarfs and Brown Dwarfs
• SDSS Data Management and Photometric Quality Assessment
• The Sloan Digital Sky Survey Monitor Telescope Pipeline
• Found: The missing blue opacity in atmosphere models of cool hydrogen white dwarfs
• Direct Detection of Galactic Halo Dark Matter
• The White Dwarf Luminosity Function from SDSS Imaging Data
• The White Dwarf Cooling Sequence of NGC6397
• Cooling Models for Old White Dwarfs
• On the Spectral Evolution of Cool, Helium-Atmosphere White Dwarfs: Detailed Spectroscopic and Photometric Analysis of DZ Stars
• The white dwarf cooling sequence in NGC 6791
• Pure hydrogen atmosphere for very cool white dwarfs
• A Survey for Cool White Dwarfs and the age of the Galactic Disc
• Cool White Dwarfs in the Sloan Digital Sky Survey
• Probing the Faintest Stars in a Globular Star Cluster
• A Very Low-Luminosity, Very Cool, DC White Dwarf
• Search for nearby stars among proper motion stars selected by optical-to-infrared photometry III. Spectroscopic distances of 322 NLTT stars
• Model Atmosphere Analysis of Two Very Cool White Dwarfs
• Discovery of New Ultracool White Dwarfs in the Sloan Digital Sky Survey
• A New Very Cool White Dwarf Discovered by the Sloan Digital Sky Survey
• Cool White Dwarfs Revisited -- New Spectroscopy and Photometry
• New UltraCool and Halo White Dwarf Candidates in SDSS Stripe 82
• On the Dissociation Equilibrium of H2 in Very Cool, Helium-Rich White Dwarf Atmospheres
• The ultra-cool white dwarf companion of PSR J0751+1807
• Discovery of an Ultracool White Dwarf Companion
• An ultra-cool white dwarf serendipitously found with COMBO-17

Cited by in corpus (23)

• SDSS-III: Massive Spectroscopic Surveys of the Distant Universe, the Milky Way Galaxy, and Extra-Solar Planetary Systems
• SEGUE: A Spectroscopic Survey of 240,000 stars with g=14-20
• A $Gaia$ Data Release 2 catalogue of white dwarfs and a comparison with SDSS
• The Kilo-Degree Survey
• Catalogs of Hot White Dwarfs in the Milky Way from GALEX's Ultraviolet Sky Surveys. Constraining Stellar Evolution
• On type Ia supernovae and the formation of single low-mass white dwarfs
• Cool DZ white dwarfs I: Identification and spectral analysis
• A Detailed Model Atmosphere Analysis of Cool White Dwarfs in the Sloan Digital Sky Survey
• Ultracool white dwarfs and the age of the Galactic disc
• On the Nature of Ultracool White Dwarfs: Not so Cool Afterall
• Visitors from the Halo: 11 Gyr old White Dwarfs in the Solar Neighborhood
• Spitzer Observations of the Oldest White Dwarfs in the Solar Neighborhood
• 11-12 Gyr old White Dwarfs 30 parsecs Away
• Extremely faint high proper motion objects from SDSS stripe 82 - Optical classification spectroscopy of about 40 new objects
• Structure and evolution of ultra-massive white dwarfs in general relativity
• Cool White Dwarfs Found in the UKIRT Infrared Deep Sky Survey
• Near-UV absorption in very cool DA white dwarfs
• Transits and Lensing by Compact Objects in the Kepler Field: Disrupted Stars Orbiting Blue Stragglers
• The brightest pure-H ultracool white dwarf
• Photometric constraints on white dwarfs and the identification of extreme objects
• New Halo White Dwarf Candidates in the Sloan Digital Sky Survey
• Cool White Dwarfs Identified in the Second Data Release of the UKIRT Infrared Deep Sky Survey
• White dwarfs in the Capodimonte deep field