CPD-56 8032: CPD-56 8032: the dust chemistry – binarity the dust chemistry – binarity

connectionconnection

Orsola De MarcoOrsola De Marco

American Museum of Natural HistoryAmerican Museum of Natural HistoryNew YorkNew York

[WC10]

[WC9]

Waters et al. (1998)

PAH PAH C-rich dustC-rich dust

SilicatesSilicatesO-rich dustO-rich dust

= O rich = C rich

Legend:

Hot C -C - AND O -O - rich dust 80% of [WCL]

6% of normal CSPN

[WCL] stars were O-rich AGB stars in the last 2000-3000 yr. The 1st 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

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)

He2-113 CPD-56 8032

De Marco et al. 2002

STIS/UV spectroscopy

CPD-56 8032 lightcurve a 5-year period?

Cohen et al. 2002

Time of HSTobservations

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?

3D nested grid models of AGB – companion common envelopes

Orbital plane

Perpendicular to orbital plane

1130 days170 days 2310 days 3250 days

De Marco & Soker 2002, De Marco et al. 2003

That's all folks!

That's all folks!

That's all folks!

Another scenario: common envelope

Tidally-destroyed Tidally-destroyed planet forms a planet forms a rotating diskrotating disk

H envelope: H envelope: O-rich, O-rich, C/O~0.4C/O~0.4

H shell sourceH shell source

He shell source:He shell source:C-rich, C/O~5 C-rich, C/O~5

CO coreCO core

De Marco & Soker (2002)

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) (1) Enhanced Enhanced dredge-up: dredge-up: He gas with He gas with

C/O>1 C/O>1 mimixes in xes in with H-with H-shell gas shell gas (C/O<1)(C/O<1)

Enriched Enriched envelope envelope departs departs

We are left with a H-poor stellar core.

He is fully mixed and He is fully mixed and there is little or no H leftthere is little or no H left

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.