Line Identification and Excitation of Autoionizing States in a Late-Type, Low Mass Wolf-Rayet Star

TL;DR

This study identifies many previously unknown spectral lines in a low-mass Wolf-Rayet star, revealing the significance of autoionizing states and resonance fluorescence in stellar wind excitation processes.

Contribution

It provides new identifications of spectral lines and highlights the role of resonance fluorescence and high wind densities in exciting emission lines in late-type Wolf-Rayet stars.

Findings

Identification of numerous C II emission lines from autoionizing levels.

Resonance fluorescence is a key process in exciting emission lines.

High wind densities enhance collisional transfers, affecting emission spectra.

Abstract

Identifications of a large fraction of previously unidentified lines in the complex spectrum of the low mass, late-type LMC [WC11] star J060819.93-715737.4 have been made utilizing electronic databases. There are an exceptionally large number of C II emission lines originating from autoionizing (ai) levels. Resonance fluorescence between the C II ground state and excited ai levels is shown to be a important photoabsorption process that is competitive with dielectronic recombination in exciting ai emission lines in stellar winds, and has broad application to many types of emission-line stars. In addition, numerous C II quartet multiplets appear in emission that are not excited directly by recombination or resonance fluorescence, signifying high wind densities in the emission region that enhance collisional transfer between doublet and quartet states.