Mid-IR (8-13$\mu$m) Images of the 21 $\mu$m, Carbon Rich Proto-Planetary Nebulae

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Session 2 -- Planetary Nebula and Supernova Remnants
Display presentation, Monday, 9:20-6:30, Pauley Room

[2.06] Mid-IR (8-13$\mu$m) Images of the 21 $\mu$m, Carbon Rich Proto-Planetary Nebulae

G.W. Hawkins, C.J. Skinner, E. Keto (IGPP/LEA/LLNL), M. Meixner, J.R. Graham (UCB), J.F. Arens, J.G. Jernigan (SSL/UCB)

We present 9.7 and 11.8 $\mu$m narrow band ($\Delta\lambda \over \lambda$= 10\%) images of three carbon rich proto-planetary nebulae (PPN): IRAS 07134+1005 (SAO 96709), IRAS 22272+5435 (SAO 34504), and IRAS 04296+3429. The images were taken at UKIRT using the Berkeley mid-IR camera which is supported by IGPP and LEA at Lawrence Livermore National Laboratory. All three objects are among the 21 $\mu$m class of proto-planetary nebulae which have a remarkable feature at 21$\mu$m of unkown origin. We discovered a toroidal dust shell around IRAS 07134 of dimensions 3.$^{\prime\prime}$4 $\times $ 3.$^{\prime\prime}$2, P.A. 30\deg and separation of the limb brightened torus peaks of $\sim$2$^{\prime\prime}$. We resolved an elliptical dust shell around IRAS 22272 of dimensions 2$^{\prime\prime} \times$1.$^{\prime\prime}$8, P.A. 30\deg. We found IRAS 0429 to be unresolved at 1.$^{\prime\prime}$2. The fact that we resolved bipolar structure in the dust shells of two carbon rich PPN confirms the trend that carbon rich PPN are bipolar. IRAS 22272 and IRAS 07134 have visually bright central stars of spectral type G5Ia and F5I. We compare these two resolved PPN with our previous observations of IRAS 21282+5050, a young carbon rich planetary nebula with a central star of spectral type O7(f)-[WC11]. We believe these three objects form an evolutionary sequence which links carbon asymptotic giant branch stars with carbon rich planetary nebulae. Estimates of the dynamical ages of these three objects are in fair agreement with a 0.6 M$_\odot$ Schonberner track.

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