Explaining the transient fast blue absorption lines in the massive binary system Eta Carinae

TL;DR

This paper combines recent spectroscopic observations with 3D hydrodynamical simulations to elucidate the transient blue absorption features in Eta Carinae, supporting a specific orbital orientation where the secondary star is in front at periastron.

Contribution

It provides new evidence linking the transient absorption lines to the orbital geometry and wind interactions in Eta Carinae, using combined observational and simulation data.

Findings

Transient blue absorption occurs only weeks before periastron.

The secondary wind passes in front of the primary near periastron.

The orbital orientation is consistent with observations and simulations.

Abstract

We use recent observations of the He I $\lambda10830 \AA$ absorption line and 3D hydrodynamical numerical simulations of the winds collision, to strengthen the case for an orientation of the semimajor axis of the massive binary system Eta Carinae where the secondary star is toward us at periastron passage. Those observations show that the fast blue absorption component exists for only several weeks prior to the periastron passage. We show that the transient nature of the fast blue absorption component supports a geometry where the fast secondary wind, both pre and post-shock material, passes in front of the primary star near periastron passage.