AAS 206th Meeting, 29 May - 2 June 2005
Session 8 Circumstellar Shells and Disks
Poster, Monday, 9:20am-6:30pm, Tuesday, 10:00am-7:00pm, May 30, 2005, Ballroom A

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[8.08] Explaining the He II Emission in Eta Carinae

K. Davidson, J. C. Martin, R. M. Humphreys (University of Minnesota), K. Ishibashi (MIT)

We report Hubble Space Telescope (HST) observations of emission in Eta Carinae near 4680 Å, presumably He II \lambda4687, which is not spatially resolved from the central star. The emission was not detected in the spectrum from 1998.0 to 2003.0, or after the spectroscopic event in 2003.5. It appeared in early 2003, rapidly grew to a larger brightness than the previous authors reported, and then disappeared suddenly near 2003.5. For several weeks the \lambda4687 luminosity was too high to explain easily in most proposed models for Eta Car's spectroscopic events. According to our analyses, this feature appears most consistent with a wind-disturbance or mass-ejection type of model with relatively high gas densities. An unusual form of radiative excitation, making use of trapped He II \lambda304 resonance photons, may have played a major role.

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The author(s) of this abstract have provided an email address for comments about the abstract: jmartin@astro.umn.edu

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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.