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G. C. Clayton, Y. Beshara, T. L. Smith (LSU), K. D. Gordon (Steward Obs.), F. Kerber (ST-ECF/ESO), W. A. Lawson (ADFA), L. Crause (Univ. Cape Town), G. Galaz (LCO), T. Rauch (Univ. Tubingen)
We will present new images of the unique reflection nebula surrounding the R Coronae Borealis Star, UW Cen. This nebula changes its appearance significantly on timescales of a year or less as different parts are illuminated by light from the central star modulated by shifting thick dust clouds near its surface. These dust clouds form and dissipate at irregular intervals causing the well-known declines in the R Coronae Borealis star lightcurve. In this way, the central star acts like a lighthouse shining through holes in the dust clouds and lighting up different portions of the nebula. The new images may enable us to use the light echo to calculate an accurate distance to UW Cen, investigate the morphology of the nebula in detail to study whether this object is related to planetary nebulae and the final helium shell flash stars and use the illumination of the nebula to discern the pattern of new circumstellar dust clouds. Understanding the RCB stars is a key test for any theory which aims to explain hydrogen deficiency in post-Asymptotic Giant Branch stars.