Measurements of the circumstellar shell geometry in IRC + 10216

Using speckle interferometric techniques, the authors have measured the spatial distribution of light in two infrared colors around the carbon star IRC +10216. At 2.2 μm the visibility data indicate that the brightness distribution is elongated at approximately P.A. = 20°. At 10.3 μm the distribution is more nearly circular. The authors have also measured phases in the image using the Knox-Thompson algorithm. The 10.3 μm one-dimensional images reconstructed from these phases and the visibilities show that the source is extended at all orientations. The 2.2 μm one-dimensional images, however, do exhibit the same departure from circular symmetry shown by the visibility data. The reconstructed images show that there is a general enhancement in the brightness distribution concentrated toward the north-northeast with the star offset to the south-southwest in the envelope.