The oxygen abundance of HE 13272326

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The oxygen abundance of HE 1327?2326

• Anna Frebel
• Research School of Astronomy Astrophysics
• The Australian National University

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Talking about C-rich stars HE 1327?2326
Frebel et al. 2005
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What about Fe II lines??
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Fe II upper limits
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Update on Fe abundance

• We have to live with the Fe I abundance for now
• LTE values
• FeI/H ?5.7 (subgiant and dwarf)
• FeII/H lt ?5.4 (subgiant)
• FeII/H lt ?5.2 (dwarf)

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OH features in the UV
O/Fe1DLTE 3.7 (subgiant)
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O triplet _at_ 7774Å
OI _at_ 6300
O/Fe lt 4.9
OI _at_ 7774
O/Fe1DLTE lt 3.1
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The O abundance
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1D vs 3D log e abundances
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The two ?5.0 stars

• have very similar abundances!
• 3D corrections for CNO are large but do not
  really change the abundance pattern
• more 3D and NLTE corrections needed
• and certainly, HE 1327?2326 is N rich!

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Iwamoto et al.
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Meynet et al.
60M? vini800km/s
Meynet et al. astro-ph/0510560
Solid circles Fe/H?6.6 with rotation
stars HE 1327?2326 Solid triangles
Fe/H?6.6 without rotation empty triangles
G77-61
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?p-process in supernovae

• Fröhlich et al. (astro-ph/0511376)
• Parameter sensitive
• Nothing is produced beyond Pd
• gt No Ba production

Isotopic abundances relative to solar abundances.
Filled circles antineutrino absorption
reactions included in nucleosynthesis Open
circles neutrino interactions are neglected
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Sr/Ba ratio
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Sr/Ba ratio in other metal-poor stars

• Star Sr/Ba Remark
• CS31082-001 -0.52 r-process star
• CS22892-052 -0.41 r-process star
• CS29497-004 -0.46 r-process star
• HE1327-2326 gt -0.3
• HE0024-2523 -1.12 s-process star
• LP625-44 -1.59 s-process star
• Conclusion Sr in HE1327-2326 was not made by
  main
• s-process. Alternatives are r-process, or weak
  s-process.

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New upper limit on Li abundance
log e (Li) lt 1.2
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Binary scenario

• HE 1327?2326 in binary system
• mass transfer from then-AGB companion
• may explain high CNO abundances
• may explain Li
• See Sudas talk! ?
• what about the Sr?
• no significant radial velocity variations yet!

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Update on radial velocity variations
ltvgt 63.6 km/s
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Conclusion

• Explanation of abundance pattern by
  pre-enrichment scenarios
• A possible explanation for the Sr is very
  promising
• Good reasons for believing HE1327?2326 is a early
  pop II star (pop II.5?)
• It may also be explained by a pop III binary
  scenario (?)
• So far absence of significant radial velocity
  variations
• If anyone has any other/additional ideas, please
  come forward! ?

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People and Papers
People
Papers
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• Thanks a lot for this
• winter-wonderful meeting!!

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Possibilities for C enrichment

• Born from C-rich material
• C from mass transfer in binary system

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1D vs. 3D CNO abundances
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Comparison with other metal-poor stars
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Stellar parameters

• BVRIK photometry Teff 6180 ? 80K
• (on Alonso et al. 1996 scale)
• Proper motion log g 3.7 or 4.5
• (subgiant or dwarf)
• Metallicity Fe/H ?5.4
• (from Fe I lines, NLTE corrected)

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Interpretation of abundance pattern

• list scenarios
• Iwamoto et al. 2005
• Meynet et al. 2005
• These scenarios help to explain the origin of
  this star

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courtesy of J. Norris
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Is HE 1327?2326 a Population II or Population III
star?

• Population III
• Following Suda et al., HE1327?2326 might be a
  member of a binary system with long-period,
  low-amplitude radial velocity signature
• C,N could be explained through mass transfer from
  a (now AGB) companion
• Li-deficiency may be explained with mass transfer
  
• Sr/Ba ratio may not be easily explained

• Population II
• Iwamoto et al. are able to reproduce the
  abundance pattern with their mixing and fallback
  model of a faint Pop III supernova
• Meynet et al. invoke massive rotating stars (e.g.
  with Fe/H?6.6) and reproduce similar CNO
  abundances
• Sr abundance could be consistent with
  pre-enrichment by a faint SN
• Li may not be easily explained

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Implications of a high O abundance

• Umeda Nomoto model happy
• Also Meynet et al. OK
• Still no radial velocity variations
• Pop III binary model less attractive, although it
  can not be excluded (yet)

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The oxygen abundance

• Subaru/HDS data So far only upper limit on
  oxygen
• New VLT/UVES data Detection of UV OH lines
• Reduction with REDUCE (Piskunov Valenti 2002)
• S/N _at_ 3100 XX (UV OH)
• S/N _at_ 6300 XX (O I)
• S/N _at_ 7780 XX (O I)
• O is key elements for origin scenarios