Imaging the time evolution of Eta Carinae's colliding winds with HST

Theodore R. Gull, Thomas I. Madura, Jose H. Groh and Michael F. Corcoran


We report new HST/STIS 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 blue-shifted emission (−400 to −200 km s−1) is symmetric and elongated along the northeast-southwest axis, while the red-shifted emission (+100 to +200 km s−1) is asymmetric and extends to the north- northwest. Comparison to synthetic images generated from a 3-D dynamical model strengthens the 3-D orbital orientation found by Madura et al. (2011), with an inclination i ≈ 138◦, argument of periapsis ω ≈ 270◦, and an orbital axis that is aligned at the same PA 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.

Reference: ApJ 743, L3
Status: Manuscript has been accepted