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NLTE abundance of Sr and Ba in the early Galaxy

NLTE abundance of Sr and Ba in the early Galaxy. Andrievsky S.M., Korotin S.A. et al. Spectral material. 35 giants 19 turn-off stars UVES VLT R = 45000, S/N is about 100 Most of the stars with [Fe/H] less than -3 dex Parameters were detrmined by:

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NLTE abundance of Sr and Ba in the early Galaxy

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  1. NLTE abundance of Sr and Ba in the early Galaxy Andrievsky S.M., Korotin S.A. et al.

  2. Spectral material • 35 giants • 19 turn-off stars • UVES VLT • R = 45000, S/N is about 100 Most of the stars with [Fe/H] less than -3 dex Parameters were detrmined by: Cayrel et al. 2004, Bonifacio et al. 2007, 2009

  3. Atomic models: Sr • Sr I – 24 levels for particle num. conservation • Sr II – 44 levels, n<13, l<5 • Sr III – ground level • 4d2D and 5p2P0 – fine structure • 330 b-b transitions • accurate rad. photoionizations are for s, p, d levels • H-like approx. – for f and g levels • accurate coll. exit. rates are for 5s2S and 5p2P0, 5d2D terms • approx. coll. exit. rates are for other levels • coll. exit. rates for forbidden trans. are with a factor 1 • coll. ionizations by electrons: yes • coll. with H atoms: yes (emp. scaling coefficient is 0.01)

  4. Sr atomic model: Grotrian diagram

  5. Sr II line parameters lambda, Å f log γrad log γVW ------------------------------------------------------ 4077.7090 7.063E-18.130 -7.70 4215.5190 3.303E-1 8.100 -7.70 10036.6530 1.219E-2 7.340 -7.63 10327.3110 7.393E-2 7.320 -7.63 10914.8870 5.754E-2 7.270 -7.63

  6. Test calculations

  7. Program star profile fitting

  8. NLTE corrections

  9. Sr abundance vs. Fe abundance

  10. Atomic models: Ba • Ba I – 31 level for particle num. conservation • Ba II–28 levels, n<12, l<5 (74 for particle num. conservation) • Ba III – ground level • 5d2D and 6p2P0 – fine structure • 91 b-b transitions • accurate rad. photoionizations are for s, p, d, f levels • H-like approx. – for g levels • accurate coll. exit. rates are for 6s2S and 6p2P0, 5d2D terms • approx. coll. exit. rates are for other levels • coll. exit. rates for forbidden trans. are with a factor 1 • coll. ionizations by electrons: yes • coll. with H atoms: yes (emp. scaling coefficient is 0.1)

  11. Ba atomic model: Grotrian diagram

  12. Ba II line parameters lambda, Å d(mÅ) f log γrad log γVW ------------------------------------------------------ 4554.03 0 0.364 8.20 -7.60 18 0.227 -34 0.137 5853.70 - 0.025 8.20 -7.19 6496.90 0 0.086 8.10 -7.47 -4 0.012 9 0.007

  13. Test calculations

  14. Program star profile fitting

  15. NLTE corrections

  16. NLTE corrections

  17. Ba abundance vs. Fe abundance

  18. Conclusions • We obtained the most reliable data on Sr and Ba abundance in the early Galaxy (age≈1 Gyr). • The Sr/Ba ratio is always higher than the main r-process ratio ([Sr/Br] = -0.31). • Three-component model is the most promising one for explaining the [Sr/Ba] ratio behaviour: • First HNe produce lighter elements including Fe. • Then high-mass SNe produce Sr (but not Ba). • After that low-mass SNe produce both Sr and Ba. • This study was partially supported by SCOPES grant. Thanks!

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