Observations of ultracool white dwarfs

Citation
Br. Oppenheimer et al., Observations of ultracool white dwarfs, ASTROPHYS J, 550(1), 2001, pp. 448-456
Citations number
21
Categorie Soggetti
Space Sciences
Journal title
ASTROPHYSICAL JOURNAL
ISSN journal
0004637X → ACNP
Volume
550
Issue
1
Year of publication
2001
Part
1
Pages
448 - 456
Database
ISI
SICI code
0004-637X(20010320)550:1<448:OOUWD>2.0.ZU;2-6
Abstract
We present new spectroscopic and photometric measurements of the white dwar fs LHS 3250 and WD 0346+246. Along with F351-50, these white dwarfs are the coolest ones known, all with effective temperatures below 4000 K. Their me mbership in the Galactic halo population is discussed, and detailed compari sons of all three objects with new atmosphere models are presented. The new models consider the effects of mixed H/He atmospheres and indicate that WD 0346+246 and F351-50 have predominantly helium atmospheres with only trace s of hydrogen. LHS 3250 may be a double degenerate whose average radiative temperature is between 2000 and 4000 K, but the new models fail to explain this object.