Nucleosynthesis in metalfree and metalpoor stars

1
Nucleosynthesis in metal-free and metal-poor
stars

• Yong-Zhong Qian
• University of MinnesotaJuly 18, 2007

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Effects of metallicity

• Star formation (Talks by Norman, Glover, Tan,
  Bromm, Omukai, Shull)
• Stellar evolution (Talks by Woosley, Yoon,
  Meynet, Ekstrom, Pols, Suda)
• Explosion and nucleosynthesis (Talks by Woosley,
  Nomoto, Herwig, Asplund, Cristallo, Campbell)
• A label to indicate time

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The case of pair-instability SN

• Possible only at 0 metallicity
• , little mass loss
  without rotation (Baraffe et al. 2001)
• Good understanding of explosion and
  nucleosynthesis (Heger Woosley 2002 Umeda
  Nomoto 2002)
• Distinct signature of nucleosynthesis

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Heger Woosley 2002
deficiency of odd Z elements
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Tumlinson et al. 2004
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Pair-instability SNe?

• Progenitors cannot be formed?
• Formed but nucleosynthetic signatures overwhelmed
  by other sources?
• Formed but mass reduced during evolution? (Talk
  by Ekstrom)
• What about the possible detection of a modern
  PI-SN? (Talk by Smith)

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Other sources at 0 metallicity

• intermediate-mass
  black holes, jet-powered explosion

abundances in ICM
Ohkubo et al. 2006
8
(continued)
abundances in extremely metal-poor stars
Ohkubo et al. 2006
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Rotating massive stars at low metallicity N
sources (Talk by Chiappini Figure from Chiappini
et al. 2006)
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Low and intermediate-mass stars at low metallicity
with rotation enhanced primary N production (C
from He burning mixed into H burning shell CN
cycle), also sources for C, O (Meynet Maeder
2002)
N yield
weighted by IMF
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Abundances in carbon-rich extremely metal-poor
stars
Meynet et al. 2006
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s-process at low metallicity
(Gallino et al. 1998)
Aoki et al. 2006
Van Eck et al. 2001
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Cosmic rays at low metallicity The puzzle of
(Talk by Asplund)
Cosmic rays or BBN with exotic particles?
corrected for
depletion
Asplund et al. 2006
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Major nucleosynthetic sources at low metallicity
massive stars

• Hydrostatic and explosive burning
• From C to the Fe group
• broadly similar yields with some important
  dependence on metallicity through mass loss,
  pre-SN structure, and details of explosion
• (Woosley Weaver 1995 Chieffi Limongi
  2002 Tominaga et al. 2007)

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Tominaga et al. 2007
Mass cut, fallback, mixing
Normal SN
HN Zn/Fe to fix Mcut(ini)
A Si burning region O/Fe
B O burning region Mg/Fe
for
only
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Deficiencies K, Sc, Ti, Mn, Co Remedies
changing or ?
Tominaga et al. 2007
Faint SN
Hypernova
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Supernova as a neutrino phenomenon
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Evolution of in the neutrino-heated ejecta
(Qian et al. 1993 Fuller Meyer 1995 Qian
Woosley 1996 McLaughlin et al. 1996)
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Qian Woosley 1996
Sensitivity of nucleosynthesis to
(Hoffman et al. 1996)
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(Pruet et al. 2005 Frohlich et al. 2006)
with neutrinos
without neutrinos
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Nucleosynthesis in proton-rich winds
(Frohlich et al. 2006 Pruet et al. 2006 Wanajo
2006)
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Dependence on number of neutrons captured per
seed (Pruet et al. 2006)
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Hoffman, Woosley, Qian 1997
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(Hoffman et al. 1997 Meyer Brown 1997
Freiburghaus et al. 1999)
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Typical Conditions in the Wind
(Witti et al. 1994 Qian Woosley 1996
Thompson et al. 2001)
Production of A 130 likely Production of A
195 uncertain
Proposed sources for A 195 modified winds
(e.g., Thompson 2003 Wanajo 2006) disk winds
(Pruet et al.03McLaughlin Surman05) ejecta
from SN fallback (Fryer et al. 2006)
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Summary

• Origin of at low metallicity still a
  puzzle (BBN or cosmic rays or ?)
• N at low metallicity indicating rotation
• Pb in metal-poor binary members indicating
  s-process at low-metallicity
• C to Fe group in metal-poor stars suggesting
  normal SN

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Summary (continued)

• abundance patterns in extremely metal-poor stars
  indicating contributions from hypernova and faint
  SN
• SN neutrinos interconvert protons and neutrons,
  thereby enabling a number of nuclei beyond the Fe
  group to be made under proton-rich conditions

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Summary (continued)

• Neutron-rich neutrino-driven winds from new-born
  neutron stars can easily produce Sr, Y, Zr, , Ag
  (A 88 - 110)
• Production of r-process elements with A up to 130
  in such winds is likely
• Where the production of r-process elements with A
  gt 130 occurs remains a mystery