Publications of the MPIfR
Optical & Infrared
Interferometry Group
G. Weigelt, R. Petrov, O. Chesneau, K.
Davidson, A. Domiciano de Souza, T. Driebe, R. Foy, D. Fraix-Burnet, T.
Gull, J. Hillier, K.-H. Hofmann, S. Kraus, F. Malbet, A. Marconi, P.
Mathias, J.-L. Monin, F. Millour, K. Ohnaka, F. Rantakyrö, A. Richichi,
D. Schertl, M. Schöller, P. Stee, L. Testi, and M. Wittkowski
VLTI-AMBER observations of Eta Carinae with
high spatial resolution and spectral resolutions of 1,500 and 10,000
Advances in Stellar Interferometry
Proceedings of SPIE: Vol. 6268, p.62682S-(1-6)
Danchi, W., Monnier, J., Schöller, M. (eds.)
Abstract
We present the first interferometric NIR observations of the LBV eta
Carinae with high spectral resolution. The observations were carried
out with three 8.2 m VLTI Unit Telescopes in the K-band. The raw data
are spectrally dispersed interferograms obtained with spectral
resolutions of 1,500 (MR-K mode) and 12,000 (HR-K mode). The
observations were performed in the wavelength range around both the He
I 2.059 µm and the Brgamma 2.166 µm emission lines. The spectrally
dispersed AMBER interferograms allow the investigation of the
wavelength dependence of the visibility, differential phase, and
closure phase of eta Car. In the K-band continuum, a diameter of
4.0±0.2 mas (Gaussian FWHM) was measured for eta Car's optically thick
wind region, whereas the Brgamma and He I emission line regions are
larger. If we fit Hillier et al. model visibilities to the observed
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
Brgammaemission lines, respectively. In the continuum near the Brgamma
line, an elongation along a position angle of 128° ± 15° was found,
consistent with previous VLTI/VINCI measurements. We find good
agreement between the measured visibilities and the predictions of the
radiative transfer model of Hillier et al. For the interpretation of
the non-zero differential and closure phases measured within the
Brgamma line, we present a simple geometric model of an inclined,
latitude-dependent wind zone. Our observations support theoretical
models of anisotropic winds from fast-rotating, luminous hot stars with
enhanced high-velocity mass loss near the polar regions.
You can get this publication ...