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Astron. Astrophys. 333, L51-L54 (1998)

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2. Observations and speckle masking results

The IRC +10 216 speckle interferograms were obtained with the 6 m telescope at the Special Astrophysical Observatory on April 3, 1996 (variability phase 0.10). The speckle interferograms were recorded with our NICMOS 3 camera through a standard [FORMULA] filter with a center wavelength of 2.17 µm and a bandwidth of 0.33 µm. 968 IRC +10 216 speckle interferograms and 1496 reference star interferograms (HIC 51133) were recorded. The observational parameters were as follows: exposure time per frame 70 ms, pixel size 14.6 mas, and seeing ([FORMULA]) [FORMULA] 2:005. Fig. 1 shows the diffraction-limited [FORMULA] image of IRC +10 216 which was reconstructed from the speckle interferograms using the speckle masking bispectrum method (Weigelt 1977 , Lohmann et al. 1983 , Weigelt 1991 ; note that the image published by Weigelt et al. (1997 ) was actually a [FORMULA] image, not an H-band image as was incorrectly printed). In addition to the dominant central object A, three bright knots (called B, C, and D) can be identified. The separation of B, C, and D from the central object are [FORMULA] mas, 137 mas, and 136 mas, respectively. The position angles of B, C, and D are [FORMULA], [FORMULA], and [FORMULA], respectively. The reconstructed image shows that the dust shell of IRC +10 216 is extremely clumpy. The asymmetry of the dominant central object suggests that there are at least two additional clouds E and F (not fully resolved) at separations much smaller than the separations of B, C, and D (i.e., at separation [FORMULA] 100 mas). The position angles of E and F are [FORMULA] [FORMULA] and [FORMULA], respectively. The objects A to F are located inside a larger nebulosity which looks like a bipolar, X-shaped nebula with an approximately NS polar axis (or position angle 10 to [FORMULA], in agreement with Kastner & Weintraub 1994 ). At the 2% intensity level the nebulosity extends over [FORMULA] in NS and [FORMULA] in EW direction. The considerable brightness of cloud B ([FORMULA] % of the total flux) can, for instance, be explained if we assume that the central star is obscured by a dust disk seen nearly edge-on. The smallest radius of the dominant central object (A+E+F) was measured for position angle [FORMULA] (see Fig. 2 a). At position angle [FORMULA] the radius of the central object was determined to be approximately 25 mas [FORMULA] 8 mas which is an upper limit for the radius of the central star, as the observed central object A could consist of both the stellar disk plus nearby or foreground dust clouds.


[FIGURE] Fig. 1a and b. Speckle masking observation of IRC +10 216: a   [FORMULA] -band speckle masking reconstruction, b  contour plot of a with the denotation of the components (the contour levels are plotted in steps of [FORMULA]). The dotted lines indicate the cut directions taken for Figs. 2 a-e

[FIGURE] Fig. 2. Intensity cuts (solid lines) through the image in Fig. 1 in the indicated directions. The cut directions are shown by dotted lines in Fig. 1 b. Dashed curves are cuts through the point spread function reconstructed from two different data sets of the reference star. In plot e the azimuthal averages of IRC +10 216 and the PSF are shown

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© European Southern Observatory (ESO) 1998

Online publication: April 20, 1998
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