Eta Carinae across the 2003.5 Minimum: Analysis in the visible and near infrared spectral region

TL;DR

This paper analyzes the visible to near-infrared spectrum of Eta Carinae during its 2003.5 minimum, providing detailed line identifications and comparing high-resolution ground-based and space-based spectra to enhance understanding of its ejecta and stellar wind features.

Contribution

It extends previous ultraviolet spectral analyses by presenting a comprehensive spectrum from 3060 to 10,430 A with line identifications and cross-instrument comparison, improving spectral interpretation of Eta Carinae.

Findings

Identification of ejecta absorption lines across the spectrum

Comparison and calibration between VLT/UVES and HST/STIS spectra

Insights into the stellar wind and circumstellar shell features

Abstract

We present an analysis of the visible through near infrared spectrum of Eta Carinae and its ejecta obtained during the "Eta Carinae Campaign with the UVES at the ESO VLT". This is a part of larger effort to present a complete Eta Carinae spectrum, and extends the previously presented analyses with the HST/STIS in the UV (1240-3159 A) to 10,430 A. The spectrum in the mid and near UV is characterized by the ejecta absorption. At longer wavelengths, stellar wind features from the central source and narrow emission lines from the Weigelt condensations dominate the spectrum. However, narrow absorption lines from the circumstellar shells are present. This paper provides a description of the spectrum between 3060 and 10,430 A, including line identifications of the ejecta absorption spectrum, the emission spectrum from the Weigelt condensations and the P-Cygni stellar wind features. The high spectral resolving power of VLT/UVES enables equivalent width measurements of atomic and molecular absorption lines for elements with no transitions at the shorter wavelengths. However, the ground based seeing and contributions of nebular scattered radiation prevent direct comparison of measured equivalent widths in the VLT/UVES and HST/STIS spectra. Fortunately, HST/STIS and VLT/UVES have a small overlap in wavelength coverage which allows us to compare and adjust for the difference in scattered radiation entering the instruments' apertures. This paper provides a complete online VLT/UVES spectrum with line identifications and a spectral comparison between HST/STIS and VLT/UVES between 3060 and 3160 A.