title: eta Carinae: Testing a Binary Orbit Model with the Hubble Space Telescope/Space Telescope Imaging Spectrograph.
abstract: Ground-based spectroscopy of eta Car shows periodic changes in some emission-line wavelengths. These variations have been cited as strong evidence that this object is a 5.5 yr binary system and have been used to produce specific orbit models. High spatial resolution data obtained with the Hubble Space Telescope/Space Telescope Imaging Spectrograph, however, do not confirm the predicted velocity behavior; therefore, the published orbit models are almost certainly invalid. Wavelength fluctuations seen at ground-based spatial resolution most likely result from other effects, which we describe. If this object is a binary system (which has not been proven), then the parameters of the secondary star and of the orbit remain largely unknown.
authors.initials: K
authors.lastname: Davidson
authors.initials: K
authors.lastname: Ishibashi
authors.initials: TR
authors.lastname: Gull
authors.initials: RM
authors.lastname: Humphreys
authors.initials: N
authors.lastname: Smith