Australia Telescope Compact Array Observations of the OH Star Roberts 22: Resolved Images of Hydroxyl Emission

Abstract

We have imaged the unusual OH/IR object G284-0.8 (Roberts 22) in the OH transitions at 1612, 1665, and 1667 MHz using the Australia Telescope Compact Array in Narrabri, NSW, Australia. The angular resolution of the OH images we present here is 6" (12,000 AU at a distance of 2 kpc). We find OH emission of extent 1.5" (2800 AU) located inside the optical bipolar flow region (size 8") discovered in the early eighties by Allen et al. and imaged recently by Sahai et al. with the Hubble Space Telescope. We present astrometry of Roberts 22, providing registration of the OH and Hubble Space Telescope images to within ~0.35". We describe the OH velocity field in Roberts 22 and discuss the kinematic properties of the source and its evolutionary status.