A NEW STUDY OF COPPER ABUNDANCES IN METALPOOR STARS

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A NEW STUDY OF COPPER ABUNDANCES IN METAL-POOR
STARS
JENNIFER SOBECK, FRANCESCA PRIMAS, CHRIS
SNEDEN EUROPEAN ORGANIZATION FOR ASTRONOMICAL
RESEARCH IN THE SOUTHERN HEMISPHERE AND THE
UNIVERSITY OF TEXAS AT AUSTIN JULY 17, 2007
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GENERAL CHARACTERISTICS OF COPPER

• Two Isoptopes 63Cu (69.17), 65Cu (30.83)
• Presence of hyperfine structure (I 3/2)
• Solar photospheric abundance log eCu 4.21
  0.04 (Anders Grevesse 1989)
• CI meteoritic abundance log eCu 4.23 0.06
  (Lodders 2003)
• 76 optical spectral transitions

Shared Upper Level

• Primary synthesis mechanisms weak s-process and
  explosive nucleosynthesis (note that minimal
  contribution occurs from main s-process
  approximately 5 Travaglio et al.2004)

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OBSERVATIONAL DATA AND THEORETICAL PREDICTIONS
FOR Cu ABUNDANCE

• LEFT PANEL Spectroscopic observations of
  Cu/Fe as a function of Fe/H for field stars
  in the Halo, thick-disk, thin-disk, Bulge-like
  stars and Omega Cen
• RIGHT PANEL Long-dashed line indicates Mej
  (Cu-weak s), Mej (Cu-SNe II), and Mej (Cu-SNe Ia)
  from Matteucci et al. 1993 short-dashed line is
  analogous with the exception of
• Mej (Cu-SNe Ia) from Iwamoto et al. (1999) and
  dotted line signifies removal of Type II SN
  contribution

Bisterzo et al. 2005, Nuc. Phys A, 758, 284
Romano Matteucci, MNRAS, 378, L59
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THEORETICAL PREDICTIONS FOR Cu ABUNDANCE

• CONCLUSION Trend in the solar vicinity
  well-reproduced metallicity-dependent yield
• CONCLUSION Initial, primary contribution
  originates from core collapse SNe and secondary
  contribution arises from the weak s-process in
  massive stars
• ODDITY Decline of Cu/Fe as a function of
  Fe/H due to reduced extent of weak s-process in
  massive stars at low Fe/H OR the delayed
  production from Type Ia SNe

Romano Matteucci, MNRAS, 378, L59
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PRIMARY MOTIVATIONS FOR NEW INVESTIGATION

• Expansion of data set to include newly-available
  spectra from a variety metal-poor star survey
  programs

• Completion of original study by Primas et al.
  reconciliation of abundances derived from
  ultraviolet and visible wavelength transitions.

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RELEVANT ATOMIC PARAMETERS FOR Cu TRANSITIONS
ULTRAVIOLET- 3247.54 Å (c 0.00 eV log (gf)
-0.048) presence of contaminant 3273.96 Å (c
0.00 eV log (gf) -0.353) OPTICAL - 5105.54 Å
(c 1.39 eV log (gf) -1.52) 5782.13 Å (c
1.64 eV log (gf) -1.72)

• REVISIONS TO THE ATOMIC PARAMETERS INCLUDE
• HYPERFINE STRUCTURE (REFERENCE Hermann et al.
  1993)
• ISOTOPIC SHIFT (REFERENCE Hermann et al. 1993)
• OSCILLATOR STRENGTHS (REFERENCE Curtis
  Theodosiou 1989)

CRITICAL COMPILATION OF TRANSITION PROBABILITY
DATA Fu et al. 1995, At. Data Nuc. Tables, 61,
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HYPERFINE STRUCTURE OF THE Cu D1 AND D2 RESONANCE
LINES
3247.54 Å FEATURE
3273.96 Å FEATURE
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SPECTRAL SYNTHESIS OF THE ULTRAVIOLET TRANSITIONS

Cu TRANSITION 3273.96 Å
Cu TRANSITION 3247.54 Å
Multiple Fe I, Eu II,
Ti II
Fe I, II
Fe I
Note that OH also has several transitions in
this wavelength regime
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SPECIAL CONSIDERATIONS
Rayleigh scattering must be taken into account in
the ultraviolet spectral range for low
temperature, low surface gravity metal-poor stars
The spectral synthesis program MOOG was altered
accordingly to incorporate a source function
which is a summation of an absorption and a
scattering component (S eB (1 - e)J). The
Short Characteristics Methodology was used in the
line transfer solution.
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DATA SET DESCRIPTION AND STELLAR ATMOSPHERIC
MODEL PARAMETERS

• DATA SAMPLE SIZE NSTARS 50
• DETECTOR/INSTRUMENT SET-UP ESO VLT 8m Kueyen
  Telescope with the Ultraviolet and Visual Echelle
  Spectrograph (UVES)
• TEMPERATURE RANGE 5530 Teff 6475 K
• SURFACE GRAVITY RANGE 3.7 lt log(g) lt 4.6
• METALLCITY RANGE -3.3 Fe/H -0.5
• SIGNAL TO NOISE RANGE 80 S/N 150 (UV) 250
  S/N 500 (Visible)
• RESOLUTION R (l/Dl) 45,000-50,000

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Cu ABUNDANCE AS A FUNCTION OF METALLICITY

• UPPER PANEL Cu/Fe as a function of Fe/H
  taken solely from the 3274 Å transition (scaling
  factor for least metal-poor targets)
• MIDDLE PANEL Inclusion of abundance due to the
  feature at 3247 Å
• LOWER PANEL Addition of data from the 5782 Å
  line

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Cu ABUNDANCE AS A FUNCTION OF STELLAR ATMOSPHERIC
PARAMETERS
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CONCLUSIONS AND FUTURE DIRECTIONS

• Improvement of branching fraction determination
  (and consequently, oscillator strength) for the
  visible wavelength transitions
• Inclusion of more abundances derived from the
  visible spectral features and expansion of the
  comparison between the Cu/Fe3274 Å and
  Cu/Fe5105 Å, 5782 Å values
• Completion of analysis of original data set
  which includes spectra from extremely metal-poor
  stars (Fe/H lt -2.8)!
• Extension of abundance determination to the
  infrared (viable transitions present beyond l
  7000 Å)
• Comparison to other Cu abundance surveys (e.g.
  Simmerer et al. 2004, Mishenina et al. 2002, )
• Determination of Zn abundances and correlation
  to Cu values
• Further elucidation of the nucleosynthesis
  mechanism (theoretical predictions)