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Session 10 - Interstellar Medium and Star Formation.
Display session, Monday, June 08
Atlas Ballroom,
We present HST WFPC2 images of IRAS 06530-0213, previously thought to be a low-mass star in the post-AGB stage of its evolution. The detection of CO maser emission from IRAS 06530 implied that this star, classified as an F0I supergiant, is accompanied by a circumstellar gaseous shell. Our HST observations show, for the first time, the circumstellar shell as seen in V and I bands. The star is surrounded by an elliptical nebula with major and minor axes of 2.^\prime\prime2 and 1.^\prime\prime3, respectively. Given an estimated distance of 10 kpc, the linear dimensions are 0.2 \times 0.1 pc. An expansion speed of a few \times 10 km s^-1 would therefore correspond to an age of a few \times 10^3 yr. The star appears highly reddened --- E(B-V)=1.5 --- both because of the cool, dusty circumstellar shell, and because of the star's location close to the galactic plane. Its appearance is also consistent with the location of this object in the IRAS color-color diagram --- in the region populated by stars at the end of their mass-loss phase.
