NUCLEOSYNTHESIS, THE RPROCESS, ABUNDANCES AND
JIM TRURAN
J. J. COWAN
University of Oklahoma
JINA Frontiers 2010 : Workshop on Nuclear Astrophysics
Yerkes Observatory - October 21, 2010
Abundance Clues and Constraints
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New observations of n-capture elements in lowmetallicity Galactic halo stars providing clues and
constraints on:
1. Synthesis mechanisms for heavy elements early in
the history of the Galaxy
2. Identities of earliest stellar generations, the
progenitors of the halo stars
3. Suggestions on sites, particularly site or sites for the
r-process
4. Galactic chemical evolution
5. Ages of the stars and the Galaxy
chronometers
Jim has contributed in all of these areas of study
r-process synthesis
2MASS View of the Milky Way
Galactic Halo Stars
• Metal-poor Halo Stars are ``fossils’’ of the Early Universe
• These Stars are Relatives of the First Stars in the Universe
back
r-Process Nucleosynthesis
• For the r-process:
• τnc << τβ decay
(typically 0.01–
0.1 s)
• Site for the
r-process still not
still not identified
Despite decades of
effort by Jim and others
Jim’s Approach to Life
Working
Playing
Most Likely Site(s) for the rProcess
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Supernovae: The Prime Suspects
Regions just outside neutronized
core: 1957 (Woosley et al. 1994;
Wanajo et al. 2002) (ν-wind)
Prompt explosions of low-mass
Type II SNe (Wheeler, JC &
Hillebrandt 1998)
He shells (Truran et al. 1978);
Jets and bubbles (Cameron 2001)
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NS & NS-BH mergers (Rosswog
et al. 1999; Freiburghaus et al.
1999)
Trying to think outside the
box
And trying not to get
tangled up in details.
n-Capture Abundances in
CS 22892-052
Historical
(~ 1996)
Even s-process
elements like
Ba made in
r-process
early in the
Galaxy.
Predicted by
Truran (1981)
Very old star.
Robust
r-process over
the history of
the Galaxy.
Very little data
then
Stellar elemental abundances consistent with scaled SS r-process only
Rare Earth Abundances in Five
r-Rich Stars: New Atomic Data
Very
little
scatter
Comparisons
of new REE
abundances
with SS
r-only
predictions
All
normalized
to Eu
Sneden et al. (2009)
CS 22892-052 Abundances
(with new atomic and stellar data)
31 N-Capture Elements Detected
The Old King
Platinum
(64 HST Orbits)
Germanium
57 elements
observed.
More than any
star except
the Sun.
Log ε(A) = Log10(NA/NH) + 12
Al Cameron Watching Over Us
Then …
And Now
New Abundance Detections of Cd
I, Lu II and Os II in BD +17 3248
Roederer
et al. (2010)
First detections of these n-cap species in metal-poor stars
Cadmium: Good in Stars, Bad in
People!
Heavy Metal: It is not as pervasive as
lead. But a study is underway to establish
safe levels of cadmium.
 McDonald’s recently recalled 12 million
Shrek-themed glasses because of concern
about the level of cadmium contained in
the enamel.

Time Magazine – July 12, 2010
Abundances in BD+17 3248: Meet
the New King!
32 n-capture elements detected in BD +17 3248
halo star to date!
Most in any metal-poor
Consistency for r-Rich Stars
CS 22892-052
HD 115444
BD +17 3248
CS 31082-001
HD 221170
HE 1523-0901
CS 22953-03
HE 2327-5642
CS 2941-069
HE 1219-0312
10 r-process rich stars
Same abundance pattern at the upper end and ? at the lower end.
But Differences Between r-rich and
r-poor Stars
r-process rich
r-process poor
Note general
fall off
Roederer et al. (2010)
incomplete
r-process
Looking at a Range of r-Process
Richness
Eu/Fe
(r-process
richness)
The ubiqiuity of the r-process (Roederer et al. 2010)
r-Process Rich vs. r-Process Poor
Origin of the Lighter n-Capture
Elements: Work in Progress
See Roederer et al. (2010)
Looking for Inspiration or
Advice?
Lighter n-Cap Element Origin?
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Weak r-process, classical wp approximation,
lower n-number densities
More sophisticated: alpha-rich freeze-out/HEW
(Kratz and Farouqi et al.) makes many of the
elements from Sr-Pd but not Ag and Cd
What about LEPP (Travaglio et al. and Montes
et al.)?
For some elements like Ge (and others?)
nu-p process (Frohlich et al. )
Maybe multiple processes?
Traveling the World
Always Willing to Pitch In
Closest Approach to a
Church
Cosmochronometers
[irrelevant;
decays too
quickly]
Rolfs & Rodney (1988)
Th Detections in Four Halo Stars
and the Sun
Note the strength
of the Th lines
independent of
metallicity
Radioactive Age Estimates

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Can use the radioactive elements (Th and U) to
make chronometric age determinations
For r-rich stars consistent abundance patterns,
excluding ``actinide boost stars’’
ages depends sensitively on observations and
production ratios
Still many uncertainties, but independent
technique generally agrees with other estimates
Note Jim’s involvement over decades
Some of Jim’s Important Papers

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Truran, Arnett & Cameron (1967) Nucleosynthesis in
Supernova Shock Waves
Arnett & Truran (1969) Carbon Burning Nucleosynthesis
at Constant Temperature
Starrfield, Sparks & Truran (1974) CNO Abundances
and Hydrodynamic Models of the Nova Outburst
Cameron & Truran (1977) The Supernova Trigger for the
Formation of the Solar System
Truran, Cowan & Cameron (1978) The Helium Driven rProcess in Supernovae
Truran (1981) A New Interpretation of the Heavy
Element Abundances in Metal-deficient Stars
Cowan, Thielemann & Truran (1991) The r-Process and
Nucleochronology
Fields, Truran & Cowan (2002) A Simple Model for rProcess Scatter and Halo Evolution
Truran et al. (2002) Probing the Neutron Capture
Nucleosynthesis History of Galactic Matter
Some Concluding Thoughts on:
Nucleosynthesis and Abundances
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r-process elements observed in very metal-poor
(old) halo stars – they are ubiquitous
Implies that r-process sites, earliest stellar
generations rapidly evolving: live and die, eject
r-process material into ISM prior to formation of
halo stars exact site still unknown
Elements (even s-process ones like Ba)
produced in r-process early in Galaxy –
predicted by JWT
Origin of lighter n-cap elements still uncertain.
Chronometers: interesting results still uncertain
JWT major contributor but lots of work to do!
With family and friends
HAPPY
TH
70
BIRTHDAY
JIM
With Collaborators at:
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U. of Texas
MSU
U. of Chicago
Caltech
MIT
Carnegie Obs.
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U. of Wisconsin
U. of Mainz
Obs. de Paris
U. of Basel
U. di Torino
ESO
With generous support from:
the National Science Foundation
& the Space Telescope Science Institute.
Rapid Neutron Capture in Type II
SNe ?
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