The brightest pure-H ultracool white dwarf
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.
Item Type | Article |
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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 |
Date Deposited | 15 May 2025 12:47 |
Last Modified | 17 Jun 2025 23:06 |
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picture_as_pdf - 906852.pdf
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