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Massive Binariesand self enrichment of globular clusters
Norbert Langer (Bonn)Onno Pols (Utrecht)
Rob Izzard (Brussels)
Selma de MinkUtrecht Bonn STScI (Nov 2010)
A&A 507, 1 (2009)Archiv: 0910.1086
S.E. de Mink
Introduction
S.E. de Mink
Multiple populations that differ in
composition and possibly in age
Globular clusters… not so simple as we thought they were
• Stellar abundancese.g. Cohen+78, Gratton+04, Carretta+09ab
• Color magnitude diagramse.g. Bedin+04, D’Antona+05, Piotto+07
Stellar rotation natural explanation some features of intermediate-age clusters?
Bastian & De Mink (2009)
S.E. de Mink
Simplified formation scenario
1. Initial cloud with “normal” composition
2. Formation of the first generation of stars
6. The multiple populations we see today.
S.E. de Mink
Simplified formation scenario
1. Initial cloud with “normal” composition
2. Formation of the first generation of stars
3. “Massive ”stars eject pro-cessed material
4. Polluting the cluster
5. Forming a second generation.
6. The multiple populations we see today.
S.E. de Mink
The polluters?
Requirements ejecta
I. Low velocity to remain within the potential well of the cluster
II. Processed by H-burning at high temperature
e.g. Prantzos+07
Challenges
• Composition
• Amount
e.g. Gratton+04, D’Antona+Caloi08
Proposed sources
I. Massive AGB stars:e.g. Cottrell+DaCosta+81,
Ventura+01
II. Spin stars:fast rotating massive stars
e.g. Decresin+07
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Mass budget
Kroupa 2001
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Mass budget
Ciotti+91, D’Ercole+08 Prantzos+Charbonnel06,
Decressin+07
Assuming all stars rotate
fast!(>0.8 break-up)
Assuming all 4-9 Msun stars ar single and contribute
Anomalous IMF ?
Strong preferential loss of normal stars ?
External pollution ?
Alterative source?
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Massive binariesstars are also ...
... not as simple as we thought they were
hoped
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- The most massive star enriches its inner layers with products of proton capture reactions.
Interacting Binaries
S.E. de Mink
- The most massive star enriches its inner layers with products of proton capture reactions.
Interacting Binaries
He core
“Strongly” processed
“Mildly” processed
Unprocessed
C↓N↑
O↓Na↑
Mg↓Al↑
Li↓
De Mink et al. (2009a)
S.E. de Mink
- The most massive star enriches its inner layers with products of proton capture reactions.
- When it expands beyond a critical radius, it is stripped from its entire envelope.
- The first non-enriched layers are accreted by the companion.
Interacting Binaries
Unprocessed
De Mink et al. (2009a)
S.E. de Mink
- The most massive star enriches its inner layers with products of proton capture reactions.
- When its expands beyond a critical radius, the is stripped from its entire envelope.
- The first non-enriched layers are accreted by the companion.
- Processed material is shedded from the system at low velocity.
Interacting Binaries
Strongly processed
Mildly processed
Unprocessed
De Mink et al. (2009a)
S.E. de Mink
I. Post-interaction: common envelope ejection Cataclysmic variables, X-ray binaries, double white dwarfs, double
neutron stars, Planetary nebulae with binary cores
II. Interacting binaries Algol type systems Tests from eclipsing binaries
Observational Evidence
Refsdal+74, Sarna93, deGreve+Linnell94, Figueiredo+94, vanRensbergen+06
e.g. Iben+Livio93
De Mink, Pols, Hilditch (2007)
“Show case”: Massive interacting binary: RY Scuti
• Circum-binary disk (1AU), Nebula (2000 AU)• Rich in He, N, Poor in O, C• Velocity 30-70 km/s• Dust and clumps
Gehrz+01, Smith+01,02,
Grundstrom+07
Evidence for mass loss from binaries
- comes from a wide variety of observed systems and- seems to be a common phenomenon.
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• 3D Hydro simulations
• Evolutionary calculations- Expansion -> contact- Spin up
Mass ejection from binaries – models
Ultich+Burger76, Flannery+Ulrich77
Packet81, Barai+04, Petrovic+05
With courtesy of D. Bisikalo
e.g. Nazarenko+Glazunova06, Zhilkin+Bisikalo09
Utrecht/Bonn binary stellar evolution code Stellar evolution, mass loss, Extensive nucleosynthetic network, Mass
and angular momentum transfer, Effects of tides, Effects of rotation
De Mink, et al. 2009b, Yoon+06, Petrovic+05, Heger+00, Langer
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Typical massive binary system: 20 Msun star with a 15 Msun comp.
in a 12 days orbit (Case B)
Primary star loses 12 Msun
- 1.5 Msun is accreted
- 10.5 Msun is ejected
Ejecta are - enriched in He, N, Na, Al
- depleted in C, O, (Mg)
Example detailed model
Ejected mass (Msun)
Rela
tive s
urf
ace
abundance
Ejected mass (Msun)
De Mink et al. (2009a)
Mass ejected slowly (Msun)
Binary 10.5Spin star 1.7
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Additional remarks
Evolution was followed until end of the evolution of the primary, but the secondary can still pollute the cluster
• as a spin star• by reverse mass transfer
We assumed slow initial rotation. Fast rotation would induce extra mixing and could pollute an even larger fraction of the envelope
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Mass Budget
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Currently not very high (among the low mass stars!)
What about the massive stars?• close binary fraction > 50%
in nearby OB associations + open clusters
• Even higher in dense cores of globular clusters?- Initial/quick Mass segregation
- Early core collapse
- Dynamical interactions of stars and gas (dissipative!)
- …
Binary fraction
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Binaries as sources of enrichment
Without commonly made assumptions
• Normal IMF• No a very high fraction of very fast rotators• No external pollution• No extreme preferential loss of 1st generation stars
De Mink et al. (2009a)
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Massive Binaries:
Assuming that the complete envelope is processed and returned and that all stars above 10 Msun are in interacting binaries
Binaries as sources of enrichmentDe Mink et al. (2009a)
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Massive Binaries:
Assuming that the complete envelope is processed and returned and that all stars above 10 Msun are in interacting binaries
Binaries as sources of enrichmentDe Mink et al. (2009a)
Binaries can return more processed mass than AGB and spin stars together.
S.E. de Mink
Intermediate mass binaries:
Lower mass stars may also provide processed material showing some of the anticorrellations produced at lower T.
Massive Binaries:
Assuming that the complete envelope is processed and returned and that all stars above 10 Msun are in interacting binaries
Binaries can return more processed mass than AGB and spin stars together.
Binaries as sources of enrichmentDe Mink et al. (2009a)
S.E. de Mink
Conclusion
• Interactions between massive stars and therefore mass stripping are likely in center of massive young clusters
• Interacting stars can eject material - processed by H-burning
- at low velocities
- in large amounts
• Possibly more important than the previously suggested sources (at least in terms of ejecta mass)
• Relieve of the need for extreme additional assumptions- a top heavy IMF
- extreme polution or preferenial mass loss
Conclusion Interacting stars are promising sources for self enrichment of globular clusters
A&A 507, 1 (2009)Archiv: 0910.1086
S.E. de MinkS. E. de Mink
A&A 507, 1 (2009)Archiv: 0910.1086