IMAGING THE TIME EVOLUTION OF ETA CARINAE'S COLLIDING WINDS WITH HST

We report new Hubble Space Telescope/Space Telescope Imaging Spectrograph observations that map the high-ionization forbidden line emission in the inner arcsecond of Eta Car, the first that fully image the extended wind-wind interaction region of the massive colliding wind binary. These observations were obtained after the 2009.0 periastron at orbital phases 0.084, 0.163, and 0.323 of the 5.54 year spectroscopic cycle. We analyze the variations in brightness and morphology of the emission, and find that blueshifted emission (–400 to –200 km s–1) is symmetric and elongated along the northeast-southwest axis, while the redshifted emission (+100 to +200 km s–1) is asymmetric and extends to the north-northwest. Comparison with synthetic images generated from a three-dimensional (3D) dynamical model strengthens the 3D orbital orientation found by Madura et al., with an inclination of i ≈ 138°, an argument of periapsis of ω ≈ 270°, and an orbital axis that is aligned at the same position angle on the sky as the symmetry axis of the Homunculus, 312°. We discuss the potential that these and future mappings have for constraining the stellar parameters of the companion star and the long-term variability of the system.