Phosphorus Abundances in the Hyades and Galactic Disk

TL;DR

This study measures phosphorus abundances in Hyades cluster and disk stars using infrared spectra, finding consistency with chemical evolution models and suggesting P is produced at the same sites as alpha elements.

Contribution

First measurement of phosphorus abundances in Hyades and disk stars using infrared P I lines, confirming their reliability and consistency with chemical evolution models.

Findings

[P/Fe] ratios are consistent with models with increased P yields.

[P/Si] ratio increases at lower [Fe/H].

[P/Fe] evolution with age resembles that of alpha elements.

Abstract

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.