Ages of White Dwarf-Red Subdwarf Systems

Abstract

We provide the first age estimates for two recently discovered white dwarf-red subdwarf systems, LHS 193AB and LHS 300AB. These unusual systems provide a new opportunity for linking the reliable age estimates for the white dwarfs to the (measurable) metallicities of the red subdwarfs. We have obtained precise photometry in the $V_J{R}_{KC}{I}_{KC}JH$ bands and spectroscopy covering from 6000Åto 9000Åfor the two new systems, as well as for a comparison white dwarf-main sequence red dwarf system, GJ 283 AB. Using model grids available in the literature, we estimate the cooling age as well as temperature, surface gravity, mass, progenitor mass and {\it total} lifetimes of the white dwarfs. The results indicate that the two new systems are probably ancient thick disk objects with ages of at least 6-9 Gyr. We also conduct searches of red dwarf and white dwarf compendia from SDSS data and the L{é}pine Shara Proper Motion (LSPM) catalog for additional common proper motion white dwarf-red subdwarf systems. Only seven new candidate systems are found, which indicates the rarity of these systems.

accepted for publication in ApJ

References in corpus (26)

• Color Transformations for the 2MASS Second Incremental Data Release
• A Catalog of Northern Stars With Annual Proper Motions Larger Than 0.15 Seconds of Arc (LSPM catalog - North)
• Photometric and Spectroscopic Analysis of Cool White Dwarfs with Trigonometric Parallax Measurements
• M-Subdwarfs: Spectroscopic Classification and the Metallicity Scale
• Spectroscopic Properties of Cool Stars in the SDSS: An Analysis of Magnetic Activity and a Search for Subdwarfs
• Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
• The White Dwarf Cooling Sequence of the Globular Cluster Messier 4
• A Catalog of Spectroscopically Identified White Dwarf Stars in the First Data Release of the Sloan Digital Sky Survey
• Direct Detection of Galactic Halo Dark Matter
• Cooling Models for Old White Dwarfs
• Disk and Halo Wide Binaries from the Revised Luyten Catalog: Probes of Star Formation and MACHO Dark Matter
• White Dwarfs in Globular Clusters: HST Observations of M4
• Detailed Spectroscopic and Photometric Analysis of DQ White Dwarfs
• The Solar Neighborhood XIII: Parallax Results from the CTIOPI 0.9-m Program -- Stars with mu >= 1"/year (MOTION Sample)
• High-velocity white dwarfs: thick disk, not dark matter
• Evolutionary calculations of phase separation in crystallizing white dwarf stars
• Probing the LHS Catalog. I. New Nearby Stars and the Coolest Subdwarf
• The Chromospheric Activity and Ages of M Dwarf Stars in Wide Binary Systems
• On the Interpretation of High Velocity White Dwarfs as Members of the Galactic Halo
• The Subdwarf Luminosity Function
• M Subdwarfs: The Population II Luminosity Function
• Cool White Dwarfs Revisited -- New Spectroscopy and Photometry
• On high proper motion white dwarfs from photographic surveys
• New metallicity calibration down to [Fe/H] = -2.75 dex
• Forever Young: High Chromospheric Activity in M subdwarfs
• A source of high-velocity white dwarfs

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• Cool Subdwarf Investigations (CSI) I: New Thoughts for the Spectral Types of K and M Subdwarfs
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• A spectroscopic and proper motion search of Sloan digital Sky Survey: red subdwarfs in binary systems
• The DODO Survey II: A Gemini Direct Imaging Search for Substellar and Planetary Mass Companions around Nearby Equatorial and Northern Hemisphere White Dwarfs
• A New Sample of Cool Subdwarfs from SDSS: Properties and Kinematics
• Mapping the Local Halo: Statistical Parallax Analysis of SDSS Low-Mass Subdwarfs
• Wolf 1130: A Nearby Triple System Containing a Cool, Ultramassive White Dwarf
• Discovery of a widely separated UCD-WD binary
• Trigonometric parallaxes of high velocity halo white dwarf candidates
• Multiplicity of the Galactic Senior Citizens: A high-resolution search for cool subdwarf companions
• Cool Subdwarf Investigations III: Dynamical Masses of Low Metallicity Subdwarfs
• Metallicity, temperature, and gravity scales of M subdwarfs
• The Solar Neighborhood XLII. Parallax Results from the CTIOPI 0.9-m Program --- Identifying New Nearby Subdwarfs Using Tangential Velocities and Locations on the H-R Diagram
• Astrophysics in 2006
• First discovery of an ultra-cool white dwarf benchmark in common proper motion with an M dwarf
• Catalogs of Wide Binaries and their Impact on Galactic Astronomy
• The Luminosity Function for White Dwarfs in the SuperCOSMOS Sky Survey