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 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 () 2:005. Fig. 1 shows the diffraction-limited 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 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 mas, 137 mas, and 136 mas, respectively. The position angles of B, C, and D are , , and , 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 100 mas). The position angles of E and F are and , 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 , in agreement with Kastner & Weintraub 1994 ). At the 2% intensity level the nebulosity extends over in NS and in EW direction. The considerable brightness of cloud B ( % 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 (see Fig. 2 a). At position angle the radius of the central object was determined to be approximately 25 mas 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.
© European Southern Observatory (ESO) 1998
Online publication: April 20, 1998