Phosphorus Abundances in the Hyades and Galactic Disk
  We have measured phosphorus abundances in nine disk stars between -1 $<$
[Fe/H] $<$ -0.5 and in 12 members of the Hyades open cluster using two P I
lines at 1.06 $\mu$m. High resolution infrared spectra were obtained using
Phoenix on Gemini South and abundances were determined by comparing synthetic
spectra to the observations. The average abundance for the dwarf stars in our
Hyades sample was $<$ [P/Fe] $>$ = -0.01 $\pm$ 0.06 and $<$ [P/Fe] $>$ = 0.03
$\pm$ 0.03 dex for the three giants. The consistency suggests abundances
derived using the 1.06 $\mu$m P I lines are not subjected to temperature or
luminosity dependent systematic effects at high metallicities. Our [P/Fe]
ratios measured in disk stars are consistent with chemical evolution models
with P yields increased by a factor of 2.75. We find [P/O], [P/Mg], [P/Si] and
[P/Ti] ratios are consistent with the solar ratio over a range of -1.0 $<$
[Fe/H] $<$ 0.2 with the [P/Si] ratio increasing by $\sim$ 0.1 - 0.2 dex at the
lowest [Fe/H] ratios. Finally, the evolution of [P/Fe] with age is similar to
other $\alpha$ elements, providing evidence that P is produced at the same
sites.
