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		| Paper: | Multi-Wavelength Implications of the Companion Star in η Carinae |  
		| Volume: | 465, Four Decades of Massive Star Research - A Scientific Meeting in Honor of Anthony J. Moffat |  
		| Page: | 313 |  
		| Authors: | Madura, T. I.; Gull, T. R.; Groh, J. H.; Owocki, S. P.; Okazaki, A.; Hillier, D. J.; Russell, C. |  
		| Abstract: | η Carinae is considered 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 as the primary dwarfs its emission at most wavelengths. Using three-dimensional SPH simulations of η Car's colliding winds and radiative transfer codes, we are able to compute synthetic observables across multiple wavebands for comparison to the observations. The models show that the presence of a companion star has a profound influence on the observed HST/STIS UV spectrum and Hα line profiles, as well as the ground-based photometric monitoring. Here, we focus on the bore-hole effect, wherein the fast wind from the hot secondary star carves a cavity in the dense primary wind, allowing increased escape of radiation from the hotter/deeper layers of the primary's extended wind photosphere. The results have important implications for interpretations of η Car's observables at multiple wavelengths. |  
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