The brightest pure-H ultracool white dwarf

S. Catalan, P. -E. Tremblay, D.J. Pinfield, Leigh Smith, Z. H. Zhang, R. Napiwotzki, F. Marocco, A. C. Day-Jones, J. Gomes, K.P. Forde, P.W. Lucas, H.R.A. Jones

Research output: Contribution to journalArticlepeer-review

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Abstract

We report the identification of LSR J0745+2627 in the United Kingdom InfraRed Telescope Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS) as a cool white dwarf with kinematics and age compatible with the thick-disk/halo population. LSR J0745+2627 has a high proper motion (890 mas/yr) and a high reduced proper motion value in the J band (H-J = 21.87). We show how the infrared-reduced proper motion diagram is useful for selecting a sample of cool white dwarfs with low contamination. LSR J0745+2627 is also detected in the Sloan Digital Sky Survey (SDSS) and the Wide-field Infrared Survey Explorer (WISE). We have spectroscopically confirmed this object as a cool white dwarf using X-Shooter on the Very Large Telescope. A detailed analysis of its spectral energy distribution reveals that its atmosphere is compatible with a pure-H composition model with an effective temperature of 3880 +/- 90 K. This object is the brightest pure-H ultracool white dwarf (T-eff <4000 K) ever identified. We have constrained the distance (24-45 pc), space velocities and age considering different surface gravities. The results obtained suggest that LSR J0745+2627 belongs to the thick-disk/halo population and is also one of the closest ultracool white dwarfs.

Original languageEnglish
Article number3
Number of pages5
JournalAstronomy & Astrophysics
Volume546
DOIs
Publication statusPublished - Oct 2012

Keywords

  • white dwarfs
  • stars: Population II
  • stars: abundances
  • stars: individual: ULAS J074509.02+262705.0
  • stars: individual: SDSS J074509.02+262705.0
  • stars: fundamental parameters
  • DIGITAL-SKY-SURVEY
  • MODEL ATMOSPHERE ANALYSIS
  • LUMINOSITY FUNCTION
  • PHOTOMETRIC SYSTEM
  • SOLAR NEIGHBORHOOD
  • NORTHERN STARS
  • 3D KINEMATICS
  • SPY PROJECT
  • CATALOG

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