The brightest pure-H ultracool white dwarf
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 (Teff<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.
Keywords
Cite
@article{arxiv.1209.1403,
title = {The brightest pure-H ultracool white dwarf},
author = {S. Catalan and P. -E. Tremblay and D. J. Pinfield and L. C. Smith and Z. H. Zhang and R. Napiwotzki and F. Marocco and A. C. Day-Jones and J. Gomes and K. P. Forde and P. W. Lucas and H. R. A. Jones},
journal= {arXiv preprint arXiv:1209.1403},
year = {2015}
}
Comments
5 pages, 7 figures, accepted for publication in A&A Letters