AGB and stardusts

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AGB and stardusts

• Roberto Gallino
• Collaborators with whom I have shared ideas,
  dreams,
• stolen plots or PhD students that I have pestered
  all the time
• M.Busso, Univ. Perugia G.Wasserburg, Caltech
  (Pasadena,CA,USA)
• A. Davis, Julia Barzyk Enrico Fermi Institute,
  Chicago
• M. Lugaro, Institute of Astronomy Utrecht (ND)
• A.Karakas Institute of Astronomy, Canberra (AUS)
• M. Pellin, M. Savina Argonne National Laboratory,
  (USA)
• E. Zinner, S.Amari, Washington Univ., St. Louis
  (USA)
• M. Pignatari, L. Husti, S. Bisterzo Torino Univ.
  
• O. Straniero, S. Cristallo Teramo Obs.

Perugia, Incontro di Astrofisica Nucleare Nov
26-27 2006
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Grains from AGB stars
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Murchison CM chondrite
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central star 1011 m, ring 1016 m
1 m
But careful with the dimensions!
10-6 m
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26Al in oxide grains

• Oxide grains reach much higher 26Al/27Al ratios
  than SiC grains from AGB stars

110-5
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26Al in oxide grains

• CBP is needed to explain the high 26Al/27Al
  ratios of oxide grains. Does CBP prevent stars
  from becoming C stars from which SiC grains can
  condense?

CBP
CBP
110-5
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Zr
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Zr composition
90Zr, 91Zr and 92Zr have or are close to have
magic number of neutrons. Their s are very low,
so they are very sensitive to the main neutron
exposure in the 13C pocket.
96Zr is produced via a branching at the unstable
95Zr, if Nn gt 5 x 108 neutrons/cm3.
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Lugaro et al., 2003, ApJ
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Lugaro et al., 2003, ApJ
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Zr composition of single SiC

The AGB star component is not constant. A wealth
of precise of information on AGB models!
Lugaro et al. 2003
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Mo
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Mo composition of single SiC
SUN
Three-isotope plots are very useful because the
composition of material produced by mixing of two
components lies on the line that connects the two
component.
mixing line
HIGH
AGB
Permil variation with respect to solar composition
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Lugaro et al., 2003, ApJ
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Lugaro et al., 2003, ApJ
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Sr
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Nicolussi et al., 1998, PRL
Lugaro et al., 2003, ApJ
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Ru Tc
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Ru in mainstream SiC grains
Comparison with AGB stellar models
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• Grains formed while 99Tc (T1/2213 ky) was still
  alive
• Tc seen in red giant stars, which pointed to them
  as the source of the s-process
• Tc-Ru isotope story in SiC grains cements the
  connection of mainstream SiC grains with AGB
  stars, the major site of the s-process

Savina et al., 2003, Science
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SiC-X grains from Supernovae Double laser
extraction with the CHARISMA Instrument (Argonne
National Laboratory)
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Lessons from X-grains

• Although previously hypothesized, a new type of
  nucleosynthesis was recognized in nature
• The neutron burst required is a natural
  consequence of Type II supernova explosions
• X-grains (at least these ones) must come from
  Type II, not Type Ia supernovae, as such a burst
  does not occur in SN Ia
• Since n-burst signature comes from an O-rich
  zone, this material must have mixed with C-rich
  matter prior to SiC condensation

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Conclusions

• Stardusts recovered from pristine Carbonaceous
  Meteorites
• carry the nucleosynthesis signature of their
  parent stars.
• Different populations have been discovered so
  far (SiC,
• graphite, diamonds, silicates, corundum,
  spinel, hibonite)
• from Red Giants, AGBs, Novae, Supernovae.
• Isotopic analysis in the laboratory of major
  elements and
• of trace elements are unique opportunities
  to test
• stellar evolution and nucleosynthesis
  theories for stars of
• different masses and metallicities.
• For light isotopes like Si, Mg, Ca, Ti stardusts
  are useful
• tools to infer the chemical evolution of the
  Galactic thin
• disk.

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Contents 1. Motivation 2. Methods 3.
Introduction 4. Results 5. Discussion 6.
Conclusions
Conclusions