The optical polarisation of RCRA and TCRA - NGC6729

Abstract

A study is presented of the reflection nebula NGC 6729, using the techniques of imaging polarimetry, with the aim of attempting to discover the geometry of the nebula and the role which each of the two stars seen within the nebula - R & T CrA - plays in its illumination. The polarisation results may be interpreted in terms of both stars having circumstellar disks, aligned parallel to one another. From observations of the total intensity of light emitted from the nebula, "jets' are observed to be emanating from the two stars. These 'jets' are interpreted as outflows of matter from the stars, and are compared with similar features noted by other observers elsewhere. These comparisons yield one major difference between the R and T CrA jets and those found elsewhere: These jets are not perpendicular to their respective circumstellar disks. Two alternative hypotheses are presented to account for this, and it is concluded that further observational evidence is required in order to decide between the two.