Astronomy & Astrophysics

Free access article

A&A 435, 1043-1061 (2005)
DOI: 10.1051/0004-6361:20041395

The sub-arcsecond dusty environment of Eta Carinae

O. Chesneau¹, M. Min², T. Herbst¹, L. B. F. M. Waters², D. J. Hillier³, Ch. Leinert¹, A. de Koter², I. Pascucci¹, W. Jaffe⁴, R. Köhler¹, C. Alvarez¹, R. van Boekel², W. Brandner¹, U. Graser¹, A. M. Lagrange⁵, R. Lenzen¹, S. Morel⁶ and M. Schöller⁶

¹ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
e-mail: chesneau@mpia-hd.mpg.de
² Sterrenkundig Instituut "Anton Pannekoek", Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
³ Department of Physics and Astronomy, University of Pittsburgh, 3941 O'Hara Street, Pittsburgh, PA 15260, USA
⁴ Leiden Observatory, Niels Bohr weg 2, 2333 CA Leiden, The Netherlands,
⁵ Laboratoire d'Astrophysique de l'Observatoire de Grenoble, Université J. Fourier, CNRS, BP 53, 38041 Grenoble Cedex 9, France
⁶ European Southern Observatory, Casilla 19001, Santiago, Chile

(Received 3 June 2004 / Accepted 8 January 2005)

Abstract
The core of the nebula surrounding Eta Carinae has been observed with the VLT Adaptive Optics system NACO and with the interferometer VLTI/MIDI to constrain spatially and spectrally the warm dusty environment and the central object. In particular, narrow-band images at 3.74 $\mu$ m and 4.05 $\mu$ m reveal the butterfly shaped dusty environment close to the central star with unprecedented spatial resolution. A void whose radius corresponds to the expected sublimation radius has been discovered around the central source. Fringes have been obtained in the Mid-IR which reveal a correlated flux of about 100 Jy situated 0 $\farcs$ 3 south-east of the photocenter of the nebula at 8.7 $\mu$ m, which corresponds with the location of the star as seen in other wavelengths. This correlated flux is partly attributed to the central object, and these observations provide an upper limit for the SED of the central source from 2.2 $\mu$ m to 13.5 $\mu$ m. Moreover, we have been able to spectrally disperse the signal from the nebula itself at PA = 318 degree, i.e. in the direction of the bipolar nebula (~310°) within the MIDI field of view of 3 $\arcsec$ . A large amount of corundum (Al₂O₃) is discovered, peaking at 0 $\farcs$ 6-1 $\farcs$ 2 south-east from the star, whereas the dust content of the Weigelt blobs is dominated by silicates. We discuss the mechanisms of dust formation which are closely related to the geometry of this Butterfly nebulae.

Key words: techniques: high angular resolution -- stars: early-type -- stars: winds, outflows -- stars: individual: Eta Carinae -- stars: circumstellar matter

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