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Georges Meynet, Sylvia Ekström, André Maeder Observatoire astronomique de l’Université de Genève

MASS LOSS INDUCED BY ROTATION AT VERY LOW METALLICITY. Georges Meynet, Sylvia Ekström, André Maeder Observatoire astronomique de l’Université de Genève Raphael Hirschi Dpt. of physics and astronomy, Basel University. Consequences for chemical enrichments.

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Georges Meynet, Sylvia Ekström, André Maeder Observatoire astronomique de l’Université de Genève

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  1. MASS LOSS INDUCED BY ROTATION AT VERY LOW METALLICITY Georges Meynet, Sylvia Ekström, André Maeder Observatoire astronomique de l’Université de Genève Raphael Hirschi Dpt. of physics and astronomy, Basel University Consequences for chemical enrichments Consequences for long GRB progenitors

  2. At low metallicity, very weak radiatively driven stellar winds Mass loss rate Kudritzki & Puls (2000)  a=0.5 Evans et al. (2005)  a=0.62+ - 0.15 What happens if metal poor stars are fast rotators ? «

  3. MORE FAST ROTATORS AT LOW Z ? Proportion of stars near break-up Increases at lower Z W/Wc = 0.7 Z=0.020  Vini= 300 - 400 km s-1 for 9 and 60 Msol Z=0 From 19 clusters in the Galaxy and the Magellanic Clouds  Vini= 500 - 800 km s-1 for 9 and 60 Msol Maeder, Grebel, Mermilliod 1999

  4. INSTABILITiES Meridional circulation Shear turbulence Zahn 1992 DEFORMATION Maeder & Zahn 1998 STELLAR WINDS Wind anisotropies Mass loss Dominiciano de Souza et al. 2003 Kippenhahn & Thomas 1970 Owocki et al. 1996; Maeder 1999 Meynet & Maeder, A&A 321, 465 (1997) Maeder & Meynet, A&A 361, 159 (2000)

  5. ! Could very low metallicity stars loose a lot of mass when reaching the break-up ?

  6. 60 Msol Z=0.0006 On Main-Sequence 20 Msol lost Non rotating model 0.8 Msol lost Decressin,Meynet,Charbonnel, Prantzos, Ekström (in prep)

  7. 60 Msol, Z=10-5, Wini/W = 0.85

  8. [Fe/H]=-6.6 300 km/s Fin MS MASSE PERDUE 800 km/s Age en millions d’années

  9. PROGENITOR OF A LONG GRB AT VERY LOW METALLICITY WO star  SN Ic Hirschi (2006) collapsar NO MAGNETIC FIELDS

  10. Vini=800 km s-1 Observations from Spite et al. (2004) Israelian et al. (2004) Vini=300 km s-1 Chiappini, Hirschi, Meynet, Ekström, Maeder, Matteucci (2006)

  11. Vini=800 km s-1 Vini=800 km s-1

  12. Carbon Rich Ultra Metal Poor Stars (CRUMPS) The most metal poor stars Norris et al 1997 See also Mc William et al 95; Barbuy et al. 96; Christlieb et al. 04; Frebel et al. 05; Plez & Cohen 05 Christlieb et al. 2002 Frebel et al. 2005

  13. Hirschi (2006) See also Meynet, Ekström, Maeder (2006)

  14. DOUBLE SEQUENCE. Blue Sequence Red Sequence [Fe/H]=-1.57 [Fe/H]=-1.26 Piotto et al., ApJ, 621, 777 (2005) Interpretation: Bedin et al. (2004)  blue sequence  pop of super-helium rich stars 2 Y=mass fraction of helium which would be necessary to reproduce the position of the blue sequence Y=0.38 Y=0.25

  15. DY/DZ 60 Msol Z = 10-8 remaining mass in solar masses

  16. CONCLUSION EFFECTS OF ROTATION AT VERY LOW METALLICITY STARS MAY LOOSE GREAT AMOUNT OF MASS BREAK-UP LIMIT REACHED REDWARDS EVOLUTION & SURFACE METALLICITY ENHANCED IMPACT ON FINAL FATE IMPACT ON THE YIELDS He, C, N, O RICH WINDS

  17. IMPACTS OF FAST ROTATION IN METAL POOR ENVIRONMENTS  Primary nitrogen production Meynet & Maeder (2002); Chiappini et al. (2006); see posters 7, 61, 211  C-rich extremely metal poor stars Meynet, Ekström, Maeder (2006), Hirschi (2006)  He-rich stars in w Cen Maeder & Meynet (2006), see poster 203  Abundance inhomogeneities in globular clusters Decressin, Meynet, Charbonnel, Prantzos, Ekström (in prep.)

  18. NUMEROUS INTERESTING CONSEQUENCES The effects of rotation are amplified at low metallicity  mixing enhanced  induce mass loss • Higher surface enrichments at low Z Maeder &Meynet 2001; Venn & Przybilla 2003 • Change with Z of populations of Be stars Maeder et al. 1999 • of blue to red supergiant ratio Langer & Maeder 1995; Maeder &Meynet 2001 • of LBV and WR stars Fliegner & Langer 1995; Meynet & Maeder 2005 • of type Ibc to II SN ratio Prantzos & Boissier 2003; Meynet & Maeder 2005 • of collapsar progenitors MacFadyen & Woosley 1999; Hirschi et al 2005 • Change with Z of the stellar yields Meynet & Maeder 2002; Ekström et al. in prep.  A LOT OF INTERESTING PROBLEMS TO STUDY…

  19. Meynet, Ekström, Maeder (2006)

  20. GLOBULAR CLUSTERS: O-poor and Na-rich stars Graton et al 2004

  21. [O/Na]

  22. Ekstroem, Meynet, Maeder 2005

  23. WHAT HAPPENS IF STARS ARE ROTATING ? ROTATION MODIFIES THE SURFACE CONDITIONS MERIDIONAL CIRCULATION TRANSPORT ANGULAR MOMENTUM OUTWARDS IN THE OUTER LAYERS ROTATION INDUCES INTERNAL CHEMICAL MIXING WHICH CHANGES THE EVOLUTIONARY TRACKS ROTATION INDUCES CHANGES OF THE SURFACE CHEMICAL COMPOSITION • FAVOURS WR STAR FORMATION 2) INCREASE THE OPACITY OF THE OUTER LAYERS TRIGGERING LINE DRIVEN WINDS

  24. STARS ARE DEFORMED ACHERNAR Dominiciano de Souza et al. 2003

  25. Domiciano de Souza et al. 2005 Tmax=8500 K Inclination=65 Ekström, Meynet, Maeder (in prep) Tmin= 6508 K Rpole/Requa=0.81 Temperature Frad~ geff=g-centrifugal force Von Zeipel theorem (1924) 6508 7172 7836 8500

  26. ROTATION  WIND ANISOTROPIES THEORY OBSERVATIONS AG Carinae Nota, 1997 Maeder, 1999 LOST LITTLE ANGULAR MOMENTUM 120 Msol, Log L/Lsol = 6.0, Teff=30 000 K, van Boekel et al. 2003 Smith et al. 2003

  27. Hirschi (2006)

  28. Evolution of Ω(r) during the Main Sequence Ω decreases inside the star Removal of angular momentum at the surface by the stellar winds Transport of angular momentum Changes of the structure  Gradients ofΩ modest  At the end of the MS, dominant effect is the local conservation of the angular momentum 20 Msol, Vini= 300 km s-1

  29. Anisotropic mass loss • Different evolution of rotation • The account for anisotropic mass • loss favours break-up Maeder, 2002

  30. WG-limit at the tip of the blue loop Redwards evolution favoured

  31. What are the effects of rotation on the Wolf-Rayet star formation process ? Hot stars  Log Teff > 4.0 Mass fraction of hydrogen At the surface below 0.4 In non-rotating models: Mass loss = the key parameter In rotating models: Rotational diffusion and mass loss Maeder 1987 Fliegner and Langer 1995 Meynet and Maeder 2003

  32. For a given metallicity, the minimum initial mass of single stars which become Wolf-Rayet star is decreased for higher rotation velocities WR lifetimes also increased for a given initial mass 22Msol 37Msol

  33. HALO STARS HALO STARS Spite et al. (2004) Israelian et al. (2004) DAMPED LYMAN ALPHA SYSTEMS Pettini et al. (2002) Dessauge et al. (2005) BLUE COMPACT DWARF GALAXIES WITH EMISSION LINES Izotov, Stasinska, Meynet, Guseva, Thuan A&A, in press, (2006)

  34. Extremely metal poor C-rich stars Frebel et al. 2005 [Fe/H]=-5.4 Plez and Cohen 2005 [Fe/H]=-4.0 Christlieb et al. 2004; Norris et al. 2001 Depagne et al. 2002; Aoki et al. 2004

  35. MIXING AND FALL BACK Umeda and Nomoto 2003 See also Iwamoto et al. 2005 Limongi et al. 2003: two SNe with proginotors of 15 and 35 Msol Suda et al. 2004: accretion from interstellar material and from a companion (an AGB star)

  36. Meynet, Ekström, Maeder (2005)

  37. 7 Msol, Z=10-5 E-AGB phase 60 Msol, Z=10-5, C-burning phase

  38. EFFECTS OF ROTATION AT VERY LOW METALLICITY ROTATIONAL MIXING 13C and 14N produced in great quantities ROTATIONAL MASS LOSS May loose half of their initial mass through stellar winds NUCLEOSYNTHESIS Pair instability supernovae avoided ?

  39. 9 Msol When Z Surface enrichments

  40. 15 Msol, Z=0.020, Vini=300 km s-1 Vitesse angulaire [10-5 sec-1] Xc: fraction de masse d’hydrogène au centre Maeder & Meynet, A&A, 440, 1041 (2005) CHAMPS MAGNETIQUES  ROTATION SOLIDE

  41. ROTATION INTERIEURE DU SOLEIL MODELE OBSERVATION r/Rsol Eggenberger, Maeder, Meynet A&A 401, 230 (2005) Profil plat entre 0.2 – 0.7 Rsol CHAMP MAGNETIQUE

  42. Hirschi et al. 2004 For Mini < MminWR ROTATION  increases 12C and 16O by about a factor 2 A non rotating ~30 Msol as a rotating 20 Msol For Mini > MminWR ROTATION  increases 4He

  43. vini/vcrit >~0.8 vini/vcrit >~0.4 vini/vcrit >~0.4 vini/vcrit >~0.4

  44. 20Msol 22Msol Mmin WNE 25Msol 40Msol Meynet and Maeder 2004

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