Polycyclic aromatic hydrocarbons orbiting HD 233517, an evolved oxygen-rich giant

M. Jura (UCLA), C.J. Bohac, B. Sargent, W.J. Forrest, J. Green D.M. Watson(Rochester), G.C. Sloan, (Cornell), F. Markwick-Kemper (Virginia), C.H. Chen, J. Najita (NOAO)

2006, ApJ Letters, 637, L45

Full manuscript available from ApJ or locally.

We report spectra obtained with the Spitzer Space Telescope in the lambda=5-35 µm range of HD 233517, an evolved K2 III giant with circumstellar dust. For lambda > 13 µm, the flux is a smooth continuum that varies approximately as nu^-5/3. For lambda < 13 µm, although the star is oxygen-rich, PAH features produced by carbon-rich species at 6.3, 8.2, 11.3, and 12.7 µm are detected along with likely broad silicate emission near 20 µm. These results can be explained if there is a passive, flared disk orbiting HD 233517. Our data support the hypothesis that organic molecules in orbiting disks may be synthesized in situ as well as having been incorporated from the interstellar medium.

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