Publications
of the
MPIfR
Optical & Infrared
Interferometry Group
P.G. Tuthill, A.B. Men'shchikov, D.
Schertl, J.D. Monnier,
W.C. Danchi, and G. Weigelt:
Bispectrum speckle interferometry of the
Red Rectangle:
diffraction-limited near-infrared images reconstructed from Keck
telescope speckle data
Astronomy & Astrophysics 389, 889 (2002)
Abstract.
We present new near-infrared (2.1-3.3µm) images of the Red Rectangle
with
unprecedented diffraction-limited angular resolutions of 46-68 mas; 4
times
higher than that of the Hubble space telescope and almost a factor of
two
improvement over the previous 6 m SAO telecope speckle images presented
by
Men'shchikov et al. (1998). The new images, which were reconstructed
from
Keck telescope speckle data using the bispectrum speckle interferometry
method,
clearly show two bright lobes above and below the optically thick dark
lane
obscuring the central binary. X-shaped spikes, thought to trace the
surface of a biconical flow, change the intensity distribution of the
bright
lobes, making them appear broadened or with an east-west double-peak in
images
with the highest resolution. The striking biconical appearance of the
Red Rectangle is preserved on scales from 50 mas to 1 arcmin and from
the visible (red) to at least 10 mic, implying that large grains of at
least several microns in size dominate scattering. The new images
supplement previous 76 mas resolution speckle reconstructions at
shorter wavelengths of 0.6-0.8µm
(Osterbart et al. 1997) and 0.7-2.2µm (Men'shchikov et al. 1998),
allowing a more detailed analysis of the famous bipolar nebula. The
intensity distribution of the images is inconsistent with a flat disk
geometry frequently
used to model the bipolar nebulae. Instead, a geometrically thick
torus-like
density distribution with bipolar conical cavities is preferred. The
extent of
the bright lobes indicates that the dense torus has a diameter of
>100 AU, for an assumed distance of 330 pc. This torus may be the
outer
reaches of a flared thick disk tapering inwards to the central star,
however
such a density enhancement on the midplane is not strictly required to
explain
the narrow dark lane obscuring the central stars.
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