منابع مشابه
A Very Low-luminosity, Very Cool, Dc White Dwarf
The star LHS 3250 is found to be a white dwarf at a distance of 30 pc. Its absolute magnitudes (MV = 15.72; Mbol = 16.2) put it among the least-luminous white dwarfs known. Its optical spectrum shows no features, indicating it has a DC classification, and it shows no detectable polarization, indicating it does not have a very strong magnetic field. However, its broadband colors show it to have ...
متن کاملA Spectroscopic Study of Cool, Field Brown Dwarf Neighbors
The Sloan Digital Sky Survey (SDSS), Two Micron Sky Survey (2MASS) and Deep Near Infrared Survey (DENIS) have already found many dozens of brown dwarfs in the late 1990s. Many of the new spectral class of L dwarfs show undepleted lithium, which indicates that their deep interiors are not hot enough to fuse protons. Methane or T dwarfs with surface temperatures near 1,000 K have also been found ...
متن کاملA Foreground Field Brown Dwarf ?
We examine recent claims that the T-type brown dwarf S Ori 053810.1-203626 (S Ori 70) is a spectroscopically verified low mass (3 −1 MJup) member of the 1–8 Myr σ Orionis cluster. Comparative arguments by Mart́in & Zapatero Osorio asserting that S Ori 70 exhibits low surface gravity spectral features indicative of youth and low mass are invalidated by the fact that their comparison object was no...
متن کاملOn the Dissociation Equilibrium of H2 in Very Cool, Helium-Rich White Dwarf Atmospheres
We investigate the dissociation equilibrium of H2 in very cool, helium-rich white dwarf atmospheres. We present the solution of the non-ideal chemical equilibrium for the dissociation of molecular hydrogen in a medium of dense helium. We find that at the photosphere of cool white dwarfs of Teff = 4000K, the non-ideality results in an increase of the mole fraction of molecular hydrogen by up to ...
متن کاملNon-Ideal Equation of State, Refraction and Opacities in Very Cool, Helium-Rich White Dwarf Atmospheres
The atmospheres of cool, helium-rich white dwarfs constitute an exotic and poorly explored physical regime of stellar atmospheres. Under physical conditions where the temperature varies from 1000K to 10000K, the density can reach values as large as 2 g/cm, and the pressure is as high as 1 Mbar, the atmosphere is no longer an ideal gas and must be treated as a dense fluid. Helium atoms become st...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Monthly Notices of the Royal Astronomical Society
سال: 2007
ISSN: 0035-8711,1365-2966
DOI: 10.1111/j.1365-2966.2007.12348.x