The sub-arcsecond dusty environment of Eta Carinae

O. Chesneau$^1$$^4$, M.~Min$^2$,
T.~Herbst$^1$, L.B.F.M.~Waters$^2$, D.J.~Hillier$^3$,
Ch.~Leinert$^1$, A.~de~Koter$^2$ et al.

$^1$ Max-Planck-Institut f\"{u}r Astronomie,
K\"{o}nigstuhl 17, D-69117 Heidelberg, Germany
\\ $^2$ 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
\\ $^4$
Observatoire de la C\^{o}te d'Azur-CNRS-UMR 6203 Avenue Copernic,
Grasse, France

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 and 4.05 micron
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
0.3" south-east of the photocenter of the nebula at
8.7 micron, 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
to 13.5 micron. 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 degree) within the
MIDI field of view of 3 arcsec. A large amount of corundum
(Al2O3) is discovered, peaking at 0.6-1.2 arcsec
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.

Reference: 2005, A&A, 435, 1043
Status: Manuscript has been accepted