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White Dwarfs in the UKIRT Infrared Deep Sky Survey Data Release 9
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
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2014 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 788, no 2, 103- p.Article in journal (Refereed) Published
Abstract [en]

We have identified 8 to 10 new cool white dwarfs from the Large Area Survey (LAS) Data Release 9 of the United Kingdom InfraRed Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS). The data set was paired with the Sloan Digital Sky Survey to obtain proper motions and a broad ugrizYJHK wavelength coverage. Optical spectroscopic observations were secured at Gemini Observatory and confirm the degenerate status for eight of our targets. The final sample includes two additional white dwarf candidates with no spectroscopic observations. We rely on improved one-dimensional model atmospheres and new multi-dimensional simulations with CO5BOLD to review the stellar parameters of the published LAS white dwarf sample along with our additional discoveries. Most of the new objects possess very cool atmospheres with effective temperatures below 5000 K, including two pure-hydrogen remnants with a cooling age between 8.5 and 9.0 Gyr, and tangential velocities in the range 40 km s(-1) <= v(tan) <= 60 km s(-1). They are likely thick disk 10-11 Gyr old objects. In addition, we find a resolved double degenerate system with v(tan) similar to 155 km s(-1) and a cooling age between 3.0 and 5.0 Gyr. These white dwarfs could be disk remnants with a very high velocity or former halo G stars. We also compare the LAS sample with earlier studies of very cool degenerates and observe a similar deficit of helium-dominated atmospheres in the range 5000 < T-eff (K) < 6000. We review the possible explanations for the spectral evolution from helium-dominated toward hydrogen-rich atmospheres at low temperatures.

Place, publisher, year, edition, pages
2014. Vol. 788, no 2, 103- p.
Keyword [en]
infrared: stars, stars: fundamental parameters, surveys, techniques: photometric, techniques: spectroscopic, white dwarfs
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:uu:diva-228702DOI: 10.1088/0004-637X/788/2/103ISI: 000337466200006OAI: oai:DiVA.org:uu-228702DiVA: diva2:734885
Available from: 2014-07-21 Created: 2014-07-21 Last updated: 2014-07-21Bibliographically approved

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Freytag, Bernd
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