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Is the 19 F problem in AGB C-stars solved ?

Is the 19 F problem in AGB C-stars solved ?. C. Abia (UGR) S. Cristallo (UGR-INAF ) K. Cunha (ORJ) P. de Laverny (OCA) I. Domínguez (UGR) K. Eriksson (Upssala) L. Gia l a n ella (Napples) K. Hinkle (NOAO) G. Imbriani (Napples) A. Recio-Blanco (OCA) V. Smith (NOAO)

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Is the 19 F problem in AGB C-stars solved ?

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  1. Is the 19F problem in AGB C-stars solved ? C. Abia(UGR) S. Cristallo (UGR-INAF) K. Cunha (ORJ) P. de Laverny (OCA) I. Domínguez (UGR) K. Eriksson (Upssala) L. Gialanella (Napples) K. Hinkle (NOAO) G. Imbriani (Napples) A. Recio-Blanco (OCA) V. Smith (NOAO) O. Straniero (OACT-INAF)

  2. 19F is a fragile element easily destroyed by p &  captures • and difficult to observe in astrophysical objects. Its origin is not very well known... - -induced spallation in SN II (Woosley et al. 1990)‏ -TP-AGB stars (Forestini et al. 1992) -Hydrostatic He-burning in heavy mass-losing WR (Meynet & Arnould 2000)‏  Chemical evolution models suggest the contribution of all the three sources (Renda et al. 2004)‏

  3. Renda et al. (2004) ...Only AGB stars show observational evidence of 19F production, (Jorissen et al. 1992)confirmed by observations in post-AGB stars and planetary nebulae(Werner et al. 2005; Zhang & Liu 2005; Otsuka et al. 2008)‏

  4. O-rich C-rich Jorissen et al. (1992)‏  MMSSSCC(N) - 19F abundances up to 30-50 solar - [F/O] vs. C/O correlation  production in TP-AGB stars

  5. 19F nuclear chain in He-burning conditions in TP-AGB stars: , 15N, 18O are needed:p & n from 14N(n,p)14C and 13C(,n)16O • 19F has primary & secondary origins (13C):at low metallicity primary source dominates  large [F/Fe] are expected Simultaneous 19F & s-element production (?)

  6. Models and observations mainly disagree in AGB C-stars 3 M TP-AGB, Z = 0.02 Lugaro et al. (2004)‏ 1.5 M TP-AGB, Z = 0.018 Goriely & Mowlavi (2000)‏

  7. ...After up-dated s-element abundances in AGB C-stars (Abia et al. 2002) C-rich AGBs  O-rich AGBs 1.5, 2 M, Z=0.006 TP-AGB FRANEC code

  8. 19F abundance determinations from rotational HF lines @ 2.3 m in intrinsic AGB C-stars • Extragalactic C-stars as main targets(Magellanic Clouds, Draco, • Carina, Ursa Minor, Sagittarius...)‏ • Galactic field AGB C-stars as calibration objects • VLT & GEMINI, R ~ 50000 • Only one proposal accepted (after 4 trials !!!) • Only 3 galactic objects observed We decided to re-analyse the Jorissen et al. (1992) FTS spectra

  9. - Spec. synthesis with the state-of-the-art C-rich atmosphere models - Up-dated atomic and molecular (C2, CN, CO, CH) line lists - HF R9 line as the main F indicator (Gustafsson et al. 2008; Plez et al. 2008) TX Psc Teff= 3100 K, [Fe/H]= -0.4C/O =1.12, 12C/13C = 42 16O/17O =1240, 16O/18O =1450 [F/Fe] = 0.5± 0.1 [F/O] = 0.2

  10. AQ Sgr Teff= 2800K, [Fe/H]=0.0 C/O = 1.17, 12C/13C = 52 16O/17O = 1200 [F/Fe] = 0.10± 0.05 [F/O] = 0.22

  11. UU Aur Teff= 2825 K, log g = 0.0, [Fe/H]= +0.06 C/O = 1.06, 12C/13C = 50, 16O/17O = 1125, 16O/18O = 1150 [F/Fe] = 0.26  0.04 [F/O] = 0.2

  12. Main Results • Mean difference in 32 stars re-analysed  [F/Fe]= +0.6 • In some stars differences up to 1 dex ! • Unable to derive 19F abundances for Mira variables(JSL did !) • J-type stars show no 19F enhancements • SC-type stars show the largests 19F enhancements (but no so large)

  13. Why ..? • Stellar atmosphere parameters....±0.2 dex, no! • Atomic line parameters...no! • Atmosphere models.... +0.1 dex • Molecular blends C2, CN, CH.....very probably ! UU Aur Wavelength (Å) log (19F) = 4.88 ± 0.04 log (19F) = 5.65 (JSL)

  14. Evidence: SC-type stars have C/O  1 Teff= 2800K, [Fe/H]=0.0 C/O = 1.01, 12C/13C = 4.5 16O/17O = 450, 16O/18O = 1600 log (Li) = 4.8 WZ Cas [F/Fe] = 1.15  0.18 [F/O] = +0.80 HF R9 19F abundance in agreement with the JSL analysis

  15. 19F vs. s-elements C(N)-stars SC-stars J stars    1.5, 2, 3 M TP-AGB Z=0.006 FRANEC code 

  16. JSL

  17. JSL

  18. C(N)-stars SC-stars J stars M, MS, S stars     11th 1.5, 2, 3 M TP-AGB Z=0.006 FRANEC code 

  19. Intrinsic AGB stars C(N)-stars SC-stars M,MS,S stars    C/O> 1 1.5, 2, 3 M TP-AGB Z=0.006 FRANEC code  C/O> 1

  20. The [F/Fe] vs. C/O correlation dissapears...for C/O > 1!!   2 M, Z=0.008 FRANEC code

  21. Summary • Extra-mixing and/or changes in reaction rates seems not • necessaryto explain 19F abundances in AGB C-stars. • 19F and s-element enhancements are correlated in intri. AGB stars. • Yet there is a problem in explaining 19F, s-element abundances and • the C/O ratios simultaneously in AGB C-stars. • SC-stars... are they in the sequence MMSSSCC? • 19F & s-element determinations in low [Fe/H] AGB C-stars • needed to evaluate the yield from AGBs and test nucleosynthesis • models!!!

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