Abstract

Multi-Wavelength Implications of the Companion Star in Eta Carinae

Thomas Madura (Max Planck Institute for Radio Astronomy)

Ted Gull (NASA/GSFC), Jose Groh (MPIfR), Stan Owocki (University of Delaware), Atsuo Okazaki (Hokkai-Gakuen University), D. John Hillier (University of Pittsburgh), Chris Russell (University of Delaware)

Eta Carinae is generally accepted to be a massive colliding wind binary system with a highly eccentric (e~0.9), 5.54-yr orbit. However, the companion star continues to evade direct detection since the primary dwarfs its emission at most wavelengths. Using 3-D SPH simulations of Eta Car’s colliding winds and various radiative transfer codes, we are able to compute synthetic observables across multiple wavebands for comparison to the available observations. In addition to allowing us to tightly constrain, for the first time, the absolute orientation and direction of the binary orbit on the sky, the models show that the presence of a companion star has a profound influence on the observed high-ionization forbidden line emission, the HST/STIS UV spectrum and H-alpha line profiles, and the ground-based photometric monitoring. These results have important implications for theories for the formation of the Homunculus nebula and interpretations of the observations that invoke a latitude-dependent primary wind.