- Количество слайдов: 31
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 l 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
2 MASS 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 identified Despite decades of effort by Jim and others
Jim’s Approach to Life Working Playing
Most Likely Site(s) for the r-Process l 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) l 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) = Log 10(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. l Mc. Donald’s recently recalled 12 million Shrek-themed glasses because of concern about the level of cadmium contained in the enamel. l 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? l l l 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 l l 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 l l l l l 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 r. Process 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 r. Process Scatter and Halo Evolution Truran et al. (2002) Probing the Neutron Capture Nucleosynthesis History of Galactic Matter
Some Concluding Thoughts on: Nucleosynthesis and Abundances l l l 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 rprocess 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: l l l U. of Texas MSU U. of Chicago Caltech MIT Carnegie Obs. l l l 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 ? back