Detection of Neutral Phosphorus in the Near Ultraviolet Spectra of Late-Type Stars

TL;DR

This study reports the first detection of neutral phosphorus lines in the near-ultraviolet spectra of late-type stars, extending phosphorus abundance measurements to lower metallicities and providing insights into its nucleosynthetic origins.

Contribution

It presents the detection of phosphorus in stars with very low metallicity and discusses the abundance trends, including corrections for optical-ultraviolet offsets, revealing phosphorus behavior in early galaxy evolution.

Findings

[P/Fe] decreases with increasing metallicity for [Fe/H]>-1.0

[P/Fe] remains roughly constant at +0.04 for [Fe/H]<-1.0

Phosphorus shows potential primary origin in massive 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, <[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.