VLTI-AMBER observations of Eta Carinae with FINITO fringe tracker and spectral resolution 12000 (Invited Paper)
Weigelt, G., Chesneau, O., Driebe, T., Foy, R., Fraix-Burnet, D., Groh, J., Hofmann, K.-H., Kraus, S., Malbet, F., Marconi, A.,
Mathias, P., Millour, F., Monin, J.-L., Petrov, R., Rantakyrö, F., Richichi, A., Schertl, D., Schöller, M., Stee, P., Testi, L., and Wittkowski, M.
Proceedings of the SPIE conference "Astronomical Instrumentation"
held in Marseille, France from June 23-28, 2008
SPIE Proceedings, Volume 7013, pg.701303 (1-11) (2008)
Abstract
We present interferometric near-infrared observations of the Luminous Blue Variable (LBV) η Car using the
Very Large Telescope Interferometer (VLTI) and the AMBER instrument of the European Southern Observatory
(ESO).1 A high spatial resolution of 5 mas (~11.5 AU) and a high spectral resolution R = λ/Δλ=1500 and
12000 were obtained. Some of the data was recorded using the fringe tracker FINITO. The observations were
obtained in the wavelength range around both the He I 2.059 μm and the Brγ 2.166 μm emission lines. The
AMBER interferograms allow the investigation of the wavelength dependence of η Car's visibility, wavelengthdifferential
phase, and closure phase. If we fit Hillier et al.2 model visibilities to the observations, we obtain
50% encircled-energy diameters of 4.2, 6.5 and 9.6 mas in the 2.17 μm continuum, the He I, and the Brγ emission
lines, respectively. In the continuum, an elongation along a position angle of 120° ± 15°
was derived from the
visibilities. The VLTI observations support theoretical models of anisotropic winds from fast-rotating, luminous
hot stars with enhanced high-velocity mass loss near the pole.
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