VLTI-AMBER observations of Eta Carinae with high spatial resolution and spectral resolutions of 1,500 and 10,000

Gerd Weigelt, Romain G. Petrov, Olivier Chesneau, Kris Davidson, Armando Domiciano De Souza, Thomas Driebe, Renaud Foy, Didier Fraix-Burnet, Ted Gull, John D. Hillier, Karl Heinz Hofmann, Stefan Kraus, Fabien Malbet, Alessandro Marconi, Philippe Mathias, Jean Louis Monin, Florentin Millour, Keiichi Ohnaka, Frederik Rantakyrö, Andrea RichichiDieter Schertl, Markus Schöller, Philippe Stee, Leonardo Testi, Markus Wittkowski

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Scopus citations


We present the first interferometric NIR observations of the LEV η 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 Brγ 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 η Car. In the K-band continuum, a diameter of 4.0 ± 0.2 mas (Gaussian FWHM) was measured for η Car's optically thick wind region, whereas the Brγ 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 Brγ emission lines, respectively. In the continuum near the Brγ 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 Brγ 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.

Original languageEnglish (US)
Title of host publicationAdvances in Stellar Interferometry
StatePublished - 2006
EventAdvances in Stellar Interferometry - Orlando, FL, United States
Duration: May 25 2006May 30 2006

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume6268 II
ISSN (Print)0277-786X


ConferenceAdvances in Stellar Interferometry
Country/TerritoryUnited States
CityOrlando, FL


  • Infrared: stars
  • Stars: individual: η Carinae
  • Stars: mass-loss, emission-line, circumstellar matter, winds, outflows
  • Techniques: interferometric, high angular resolution, spectroscopic


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