Parallax and Luminosity Measurements of an L SubDwarf
Abstract
The lowest luminosity stars and brown dwarfs are among the most useful probes of planetary, stellar, and Galactic processes. With hydrogen-burning lifetimes far in excess of a Hubble time and space densities that exceed those of hotter stars, low-mass dwarfs are ubiquitous in the disk, thick-disk, and halo populations and may host the bulk of terrestrial planets in the Galaxy. The steady cooling of brown dwarfs over time makes them useful chronometers for coeval clusters. Observations of cool brown dwarfs provide empirical constraints on atmospheric chemical models, opacities, and dynamics and facilitate studies of hot exoplanetary atmospheres. We present the first parallax and luminosity measurements for an L subdwarf, the sdL7 2MASS J05325346+8246465. Observations conducted over 3 years by the USNO infrared astrometry program yield an astrometric distance of 26:7 +/- 1:2 pc and a proper motion of 2:624100" +/- 0:0018" yr(exp -1). Comparison of the luminosity of 2MASS J05325346+8246465 to theoretical evolutionary models indicates that its mass is just below the sustained hydrogen-burning limit, and is therefore a brown dwarf. Its kinematics are consistent with membership in the inner halo population, making this source the first bona fide halo brown dwarf. Further investigation of 2MASS J0532+8246 should be directed toward determining its metallicity and chemical abundances. Its as yet unknown subsolar metallicity remains the primary limitation in constraining its mass; determination of both parameters would provide a powerful test of interior and evolutionary models for low-mass stars and brown dwarfs.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 10, 2008
- Accession Number
- ADA640864
Entities
People
- Adam J. Burgasser
- Arne A. Henden
- Blaise C. Canzian
- Christian B. Luginbuhl
- Frederick J. Vrba
- Harry H. Guetter
- Jeffrey A. Munn
- Sebastien Lepine
Organizations
- United States Naval Observatory Flagstaff Station