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THE FIRST STARS: Uranium-rich metal-poor star CS 31082-001

THE FIRST STARS: Uranium-rich metal-poor star CS 31082-001. HST – STIS 45 orbits – 43 completed PI: Roger Cayrel (2001 – 2004) Useful range: 250-310nm, R~30,000

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THE FIRST STARS: Uranium-rich metal-poor star CS 31082-001

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  1. THE FIRST STARS: Uranium-rich metal-poor star CS 31082-001

  2. HST – STIS 45 orbits – 43 completed • PI: Roger Cayrel (2001 – 2004) • Useful range: 250-310nm, R~30,000 • B. Barbuy, M. Spite, V. Hill, F. Primas, B. Plez, C. Sneden, F. Spite, T.C. Beers, J. Andersen, B.Nordstrom, P. Bonifacio, P. François, P. Molaro, C. Siqueira-Mello

  3. Evolution of Universe vs. redshift

  4. The first generation of stars was never • observed but should be detected in 2 ways: • High mass stars explode as supernovae • and produce a GRBs (z ~ 15 ?) • GRB at z~8.2 = pop. III? • First generations of low mass stars should • be still evolving, identified by a very low • metallicity (or no metals) (z ~ 5 to 15)

  5. First Detection of Uranium in an old star Cayrel et al. 2001, Nature CS31082-001 14 +-3 Gyr Now: 3 such stars detected

  6. Neutron-capture elements are formed through the s- and r-processes. For example, in the solar system: Barium = 15% r + 85% s Europium = 97.3% r + 2.7% s In metal-poor stars, however, only the r-fraction produced in the first SNae is present. r-process site(s): not yet confirmed

  7. Beers & Christlieb 2005, ARA&A

  8. So far, 12 r-II stars (Hayek et al. 2009) 6 with well-detected Thorium 3 (2) stars with Uranium detected: ● CS 31082-001 (Cayrel et al. 2001; Hill et al. 2002) ● HE 1523-0901 (Frebel et al. 2007) ● BD+17º3248 (Cowan et al. 2002)

  9. USE OF STIS SPECTRUM IN ORDER TO: ●Measurements of new elements, in parti- cular the heaviest elements near the actinides U, Th: Bi, and Pb, produced in the same r-process event  better age derivation ●Other dominantly r-elements: Eu, Os, Ir ● New elements in the other r-process peaks

  10. 3rd peak elements and actinides LOG A(X) Z Sun VLT HST [X/Fe] Os 76 1.40 0.43 0.43 +1.30 Ir 77 1.38 0.20 0.20 +1.75 Pt 78 1.62 ---- 0.65 +1.93 Au 79 1.01 ---- -0.40 +1.58 Pb 82 1.75 -0.55 -0.65 +0.50 Bi 83 0.71 ---- -0.50 +1.54 Th 90 0.06 -0.98 ------ +1.86 U 92 -0.54 -1.92 ------ +1.52

  11. There are 3 types of chronometers involving U, Th radioactive elements (Cayrel et al. 2001, Nature, 409, 691):

  12. Using different production ratios (PRs) U/Th gives ages of 13.9 to 15.7 Gyr PRs for U/Os, U/Ir, U/Pt, U/Au, U/Bi  more uncertain

  13. AGES (Gyr) U/Os 11.5 Schatz02 U/Ir 11.7 Wanajo02 U/Pt 11.8 Wanajo02 U/Au 9.7 Wanajo07a U/Bi 13.8 Wanajo07b U/Th 13.95 Goriely01 U/Pb 11.8 Wanajo07b

  14. Roederer et al. 2009 : universality of abundance pattern of heavy r-process elements applies to Ba to Pt. It seems not to extend to Pb and beyond. 4 stars were found to show actinides boost: CS30306-132, [Fe/H]=-2.97 (Honda) CS31078-018, [Fe/H]=-2.85 (Lai) HE1219-018, [Fe/H]=-2.42 (Jonsell) CS31082-001, [Fe/H]=-2.9 (Hill)  so far this is not understood

  15. Conclusions: ● First measurement of Bi, Au ● Lowest metallicity oldest stars = laboratories for insights into the r-process nucleosynthesis ● STIS UV spectrum: legacy for atomic physics in terms of lines of heavy elements and FeII ● Independent constraint on the age of the oldest stars

  16. SCIENCE: r-process site identification and calculations of r-elements production: Among the 11 greatest unanswered Questions in Physics

  17. NEXT STEPS: • For a better understanding of the r-process: • 1st peak: 38Sr, 39Y, 40Zr, 41Nb, 42Mo • 44Ru, 45Rh, 46Pd, 47Ag, 48Cd • Electron-capture supernovae (ECSNe), with • O-Ne-Mg cores of small mass (~1.38M☺ ) • high Sr-Y-Zr, Zn low heavies • or • High mass stars with rotation (Geneva)

  18. 2nd peak would complete the r-process scenario: Ba, La, Ce, Pr, Nd, Sm, EU => optical In the STIS region: a wealth of lines of: Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu

  19. The End

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