Detection of Neutral Phosphorus in the Near Ultraviolet Spectra of
  Late-Type Stars
  We report the detection of several absorption lines of neutral phosphorus (P,
Z=15) in archival near ultraviolet spectra obtained with the Space Telescope
Imaging Spectrograph on board the Hubble Space Telescope. We derive phosphorus
abundances or interesting upper limits in 14 late-type stars with metallicities
spanning -3.8<[Fe/H]<-0.1. Previously, phosphorus had only been studied in
Galactic stars with -1.0<[Fe/H]<+0.3. Iron lines reveal abundance offsets
between the optical and ultraviolet regions, and we discuss and apply a
correction factor to account for this offset. In stars with [Fe/H]>-1.0, the
[P/Fe] ratio decreases toward the solar value with increasing metallicity, in
agreement with previous observational studies. In stars with [Fe/H]<-1.0,
<[P/Fe]>=+0.04+/-0.10, which overlaps with the [P/Fe] ratios found in several
high-redshift damped Lyman-alpha systems. This behavior hints at a primary
origin in massive stars.
