3D radiative transfer simulations of Eta Carinae's inner colliding winds - I. Ionization structure of helium at apastron

Understand

The highly eccentric binary system Eta Carinae shows numerous time-variable emission and absorption features.

• These observational signatures are the result of interactions between the complex three-dimensional (3D) wind-wind collision regions and photoionization by the luminous stars.
• Specifically, helium presents several interesting spectral features that provide important clues on the geometry and physical properties of the system and the individual stars.
• We use the SimpleX algorithm to post-process 3D smoothed particle hydrodynamics simulation output of the interacting winds in Eta Car in order to obtain the fractions of ionized helium assuming three different primary star mass-loss rates.