The results of a 7-epoch interferometric imaging study , at wavelengths in the near-infrared K-band , of the carbon star IRC +10216 are presented .
The use of non- and partially-redundant aperture masking techniques on the 10-m Keck-I telescope has allowed us to produce images of the innermost regions of the circumstellar dust envelope with unprecedented detail .
With roughly twice the resolving power of previous work ( ( ( Weigelt et al .
1997 ) ) ; ( ( Weigelt et al .
1998 ) ) ; ( ( Haniff & Buscher 1998 ) ) ) , the complex asymmetric structures reported within the central 0 \farcs 5 ( \sim 20 R _ { \star } ) have been imaged at the size scale of the stellar disk itself ( \sim 50 mas ) .
A prominent dark lane at a position angle of approximately 120 ^ { \circ } is suggested to be an optically thick disk or torus of dust which could help to explain IRC +10216 ’ s well-known bipolarity at a position angle of \sim 20 ^ { \circ } .
Observations spanning more than a pulsational cycle ( \sim 638 days ) have revealed significant temporal evolution of the nebula , including the outward motion of bright knots and clumps .
Registering these displacements against the compact bright core , which we tentatively identify as marking the location of the star , has allowed us to determine the apparent angular velocity at a number of points .
The magnitudes of the proper motions were found to be in agreement with current estimates of the stellar distance and radial velocity .
Higher outflow speeds were found for features with greater separation from the core .
This is consistent with acceleration taking place over the region sampled by the measurements , however alternate interpretations are also presented .
Although a number of changes of morphology were found , none were clearly interpreted as the condensation of new dust over the pulsation cycle .
Unfortunately , ambiguities associated with the true three-dimensional nature of the nebula weaken a number of our quantitative and qualitative conclusions .