1. CPD-56 8032: the dust chemistry – binarity connection Orsola De Marco American Museum of Natural History New York

2. [WC10] [WC9] Waters et al. (1998) PAH C-rich dust Silicates O-rich dust = O rich = C rich Legend: C -O - Hot C - AND O - rich dust 80% of [WCL] 6% of normal CSPN

3. [WCL] stars were O-rich AGB stars in the last 2000-3000 yr. The 1 st TP to make the star C-rich, also caused AGB departure. (Waters et al. 1998, Cohen et al. 1999). This is not supported by evolutionary models. (Herwig 1999, 2000, priv. comm.) Single star interpretation

4. Alternative interpretation O-rich dust disk predating the AGB star (Oort cloud). (e.g. Cohen et al. 1999) O-dust disk forms during the early AGB (binary action). (e.g. Cohen et al. 2002, De Marco et al. 2002)

5. He2-113 CPD-56 8032

6. De Marco et al. 2002 STIS/UV spectroscopy

7. CPD-56 8032 lightcurve a 5-year period? Cohen et al. 2002 Time of HST observations

8. Interpret: Binary with circumbinary disk: orbiting clumps, orbiting CPD, precessing disc. Generalize: [WC] have binary outside common envelope, make disk, star becomes [WC] by normal single star scenario or binary-enhanced mass-loss. However: Why are there no more “double-dust” normal CS? Might we not expect more bipolar PNe around [WC]s? Why are there are binary normal CS. Alternative: Some phenomenon leading to “double dust” AND [WC] star. Common envelope?

9. 3D nested grid models of AGB – companion common envelopes Orbital plane Perpendicular to orbital plane 1130 days 170 days 2310 days 3250 days De Marco & Soker 2002, De Marco et al. 2003

10. That's all folks!

13. Another scenario: common envelope Tidally-destroyed planet forms a rotating disk H envelope: O-rich, C/O~0.4 H shell source He shell source: C-rich, C/O~5 CO core De Marco & Soker (2002)

14. Convection between the H and He shell is enhanced by shear mixing and helium mixes in with the hydrogen. Mass-loss from the envelope is enhanced. (1) Enhanced dredge-up: He gas with C/O>1 mixes in with H-shell gas (C/O 1 mixes in with H-shell gas (C/O<1) Enriched envelope departs

15. We are left with a H-poor stellar core. He is fully mixed and there is little or no H left

16. The physics: Is this possible? Can we test it observationally? Shape of the PN, lack of binarity for [WC] central stars, possible abundance anomalies. The precondition: At least 12% of all stars that form PNe have companions in the mass- range 0.001-0.1Mo at distances 3-10AU.