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N. Smith (U. Colorado), J.A. Morse (Arizona State U.), N.R. Collins, T.R. Gull (NASA/GSFC)
We present UV images of Eta Carinae taken with the ACS/HRC camera on HST before, during, and after the most recent "spectroscopic event" that occurred in mid 2003, providing strong support for the idea that Eta Car may be a binary system. These multi-epoch images reveal variability in the fuzzy UV excess emission around the star called the "Purple Haze", which is a combination of circumstellar nebulosity and spatially-resolved emission from outer parts of the stellar wind. The brightness fluctuations are caused by variable UV illumination of this material during Eta Car's 5.5 yr cycle. The observed variability is decidedly asymmetric, and could be interpreted as support for the hypothesis that Eta Car is a close binary system where UV radiation from a hot companion is blocked in certain directions by the dense primary star's wind near periastron. In order to explain these changes with a single-star model, a complicated shell ejection with preferred azimuthal directions would need to be invoked.
The author(s) of this abstract have provided an email address for comments about the abstract: nathans@colorado.edu
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Bulletin of the American Astronomical Society, 36 #2
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