White dwarfs in the UKIRT infrared deep sky survey data release
- Space Telescope Science Institute, 700 San Martin Drive, Baltimore, MD 21218 (United States)
- Gemini Observatory, Northern Operations Center, 670 North A'ohoku Place, Hilo, HI 96720 (United States)
- Instituto de Astrofísica de Canarias (IAC), C/Vía Láctea s/n, E-38200 La Laguna, Tenerife (Spain)
- Astronomical Observatory, Uppsala University, Regementsvägen 1, Box 515, SE-75120 Uppsala (Sweden)
- Département de Physique, Université de Montréal, C. P. 6128, Succursale Centre-Ville, Montréal, QC H3C 3J7 (Canada)
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{sup –1} ≤v {sub tan} ≤ 60 km s{sup –1}. They are likely thick disk 10-11 Gyr old objects. In addition, we find a resolved double degenerate system with v {sub tan} ∼ 155 km s{sup –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 {sub eff} (K) < 6000. We review the possible explanations for the spectral evolution from helium-dominated toward hydrogen-rich atmospheres at low temperatures.
- OSTI ID:
- 22356622
- Journal Information:
- Astrophysical Journal, Vol. 788, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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