Atmospheric Options

In nubibus (In the clouds)

The WD program has seen two enhancements for stellar atmospheres. The earlier one was implemented in WD9 5 (and carried through WDx2 0 07); in 2003 another was integrated directly into the WD code by Van Hamme & Wilson (2003). Both are based on Kurucz's stellar atmospheres models contained on a CD-ROM4 made available by Robert L. Kurucz.

Kurucz's new stellar atmospheres incorporate computed opacities from a comprehensive list of 58 million lines. The opacities were computed for 56 temperatures in the range 2,000 to 200,000 K, 21 values of the log of the pressure (measured in cgs units) over the range -2 to +8, and 5 values ofmicroturbulent velocity (0, 1, 2, 4, and 8 km/s). They include ranges of abundances: 20 models in the range [Fe/H]5 = +1.0 to -5.0, and for 0.0 with no helium. The new line opacities and added continuous opacities were all included in the new atmosphere calculations. Temperature ranges depend on log g and abundance [M/H], with the largest range from 3,500 to 50,000 K. Temperature limits and the 19 abundances are given in Kurucz (1993).

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