The brightest pure-H ultracool white dwarf

October 2012 • 2012A&A...546L...3C

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

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.

Based on observations made with ESO telescopes at the Paranal Observatory under programme ID 088.C-0048(B).FITS version of the reduced spectrum is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/546/L3

Links

• PREPRINT http://arxiv.org/abs/1209.1403
• POSTSCRIPT https://www.aanda.org/10.1051/0004-6361/201220191/postscript
• ELECTR https://doi.org/10.1051%2F0004-6361%2F201220191
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2012A%26A...546L...3C
• PDF https://www.aanda.org/10.1051/0004-6361/201220191/pdf
• DATA http://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/546/L3
• DATA http://archive.eso.org/bin/ads2eso?2012A%26A...546L...3C
• DATA https://irsa.ipac.caltech.edu/bibdata/2012/C/2012A&A...546L...3C.html