VLTI-AMBER Observations of η Carinae with High Spatial Resolution and Spectral Resolutions of λ/Δλ=1500 and 12 000^*

We report spectro-interferometric observations of the Luminous Blue Variable (LBV) η Car using the AMBER instrument of ESO’s Very Large Telescope Interferometer (VLTI) 1. The observations around the He I 2.059 μm and the Brγ 2.166 μm emission lines allow us to investigate the wavelength dependence of the visibility, differential phase, and closure phase of η Car’s stellar wind region. If we fit visibility profiles derived from Hillier et al. models 2 to the AMBER visibilities, we obtain 50% encircled-energy diameters of 4.3, 6.5, and 9.6 mas in the 2.17 μm continuum, the He I, and the Brγ emission lines, respectively. For the interpretation of the non-zero differential and closure phases measured within the Brγ line, we developed a simple wind model. Our observations support theoretical models of winds from fast-rotating, luminous hot stars.