منابع مشابه
Heavy element abundance patterns in hot DA White Dwarfs
We present a series of systematic abundance measurements for 25 hot DA white dwarfs in the temperature range ~20000-110000K, based on far-UV spectroscopy with STIS/GHRS on HST, IUE and FUSE. Using our latest heavy element blanketed non-LTE stellar atmosphere calculations we have addressed the heavy element abundance patterns making completely objective measurements of abundance values and upper...
متن کاملChemical Abundance Constraints on White Dwarfs as Halo Dark Matter
We examine the chemical abundance constraints on a population of white dwarfs in the Halo of our Galaxy. We are motivated by microlensing experiments which have reported evidence for massive compact halo objects (Machos) in the Halo of our Galaxy, with an estimated mass of (0.1 − 1)M⊙; the only conventional dark astrophysical candidates for objects in this mass range are white dwarfs. However, ...
متن کاملThe abundance of brown dwarfs
The amount of mass contained in low-mass objects is investigated anew. Instead of using a mass–luminosity relation to convert a luminosity function to a mass function, I predict the mass-luminosity relation from assumed mass functions and the luminosity functions of Jahreiss &Wielen (1997) and Gould, Bahcall & Flynn (1997). Comparison of the resulting mass–luminosity relations with data for bin...
متن کاملAccreting White Dwarfs
Thermonuclear (type Ia) supernovae are explosions in accreting white dwarfs, but the exact scenario leading to these explosions is still unclear. An important step to clarify this point is to understand the behaviour of accreting white dwarfs in close binary systems. The characteristics of the white dwarf (mass, chemical composition, luminosity), the accreted material (chemical composition) and...
متن کاملLight Element Abundance Patterns in the Orion Association : I ) HST Observations of Boron in G - dwarfs
The boron abundances for two young solar-type members of the Orion association, BD -6 1250 and HD294297, are derived from HST STIS spectra of the B I transition at 2496.771 Å. The best-fit boron abundances for the target stars are 0.13 and 0.44 dex lower than the solar meteoritic value of log ǫ(B)=2.78. An anticorrelation of boron and oxygen is found for Orion when these results are added to pr...
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ژورنال
عنوان ژورنال: Symposium - International Astronomical Union
سال: 1991
ISSN: 0074-1809
DOI: 10.1017/s007418090022754x