Neon Abundances from a Spitzer/IRS Survey of Wolf-Rayet Stars

TL;DR

This study measures neon abundances in Wolf-Rayet stars using Spitzer spectral data, revealing solar-like levels in WN types and higher-than-solar levels in WC types, advancing understanding of stellar wind compositions.

Contribution

First to derive neon ion fractions in Wolf-Rayet stars using high-resolution infrared spectroscopy from Spitzer.

Findings

Neon abundances in WN stars are consistent with solar values.

Neon abundances in WC stars exceed solar levels.

Ion fraction abundances vary across different Wolf-Rayet subtypes.

Abstract

We report on neon abundances derived from {\it Spitzer} high resolution spectral data of eight Wolf-Rayet (WR) stars using the forbidden line of [\ion{Ne}{3}] 15.56 microns. Our targets include four WN stars of subtypes 4--7, and four WC stars of subtypes 4--7. We derive ion fraction abundances $\gamma$ of Ne^{2+} for the winds of each star. The ion fraction abundance is a product of the ionization fraction $Q_{\rm i}$ in stage i and the abundance by number ${\cal A}_E$ of element E relative to all nuclei. Values generally consistent with solar are obtained for the WN stars, and values in excess of solar are obtained for the WC stars.