Detection of Neutral Phosphorus in the Near-ultraviolet Spectra of Late-type Stars

Abstract

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, lang[P/Fe]rang = +0.04 ± 0.10, which overlaps with the [P/Fe] ratios found in several high-redshift damped Lyman-α systems. This behavior hints at a primary origin in massive stars.

Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. This work is supported through program AR-13246 and is based on observations associated with programs GO-7348, GO-7433, GO-8197, GO-9048, GO-9049, GO-9455, GO-9804, GO-12268, GO-12554, and GO-12976. Portions of this work are based on data obtained from the European Southern Observatory (ESO) Science Archive Facility. These data are associated with Programs 065.L-0507(A), 067.D-0439(A), 072.B-0179(A), 074.C-0364(A), 076.B-0055(A), and 266.D-5655(A). Portions of this research have also made use of the Keck Observatory Archive (KOA), which is operated by the W.M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration. These data are associated with Programs H2aH (P.I: Boesgaard), H5aH (P.I: Stephens), and H47aH (P.I: Boesgaard). Other portions of this work are based on data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile, and the McDonald Observatory of The University of Texas at Austin.