View
214
Download
0
Tags:
Embed Size (px)
Citation preview
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.