2. Discussions about Z effects on the Conti scenario Geneva, 1983

3. Peter sitting on pure Z=1 materials in Arapahoe Peak Boulder, 1989

4. Peter during a bicycle trip Geneva 2002

5. Peter with some of his many disciples… Boulder, 2003

6. MASSIVE STARS EVOLUTION in collaboration with : Georges Meynet Raphael Hirschi (Univ. Keele) Patrick Eggenberger (Univ. Liege) Sylvia Ekström Cyril Georgi

7. MASSIVE STARS: MASS LOSS : MIXING: shear ~ thermal diffusivity High T Low  Mass loss and mixing strongly favoured !

8. Huang & Gies (2006); see also Conti & Ebbets 1977 - Peak of V rot = 200 km/s STRUCTURE Oblateness MASS LOSS Enhanced winds Anisotropies MIXING Meridional circul. Shears Hzt. turbulence Rotation in B stars Both effects interact: - Mass loss removes angular momentum - Rotation enhances the M- loss rates

9. ROTATIONAL DISTORTION ACHERNAR ~9.6 M sol Domiciano de Souza et al. 2003 : difficulty ? Carciofi et al. 2008: equatorial disk R e /R p =1.5 ROCHE MODEL OK for ω =0.992

10. F rad  g eff  T eff ~ g eff 1/4 Von Zeipel (1924)

11. Confirmation of Von Zeipel Peterson et al. 2006 Monnier et al. 2007 T eff (pole)/T eff (equateur)=1.23-1.27 GRAVITY DARKENING Altair 1.8 M sol ω =0.9 The exponent may be smaller ~0.19 Monnier, 2007

12. iso mass loss Owocki 1996, Maeder, 1999 STELLAR WINDS & ROTATION Enables a massive star to lose lots of mass and little angular momentum  GRBs

13. ACHERNAR HAS POLAR WINDS Meilland et al. 2007 Polar mass flux 7 10 -9 M sol y -1 sr -1 Mass of the disk =4.1 10 -10 M sol Mass loss =1.3 10 -8 M sol /y Disk in Keplerian rotation Intensity map in the continuum at 2.15 micron (SIMECA code) 9.6 M sol V e =470 km/s ~91% V crit

14. (N/H) depend on - v sin i - M - age - Z, etc… SURFACE ENRICHMENTS

15. « The observation challenges the concept of rotational mixing » Hunter et al. 2008 Stars in extended regions around N11 and NGC 2004 in the LMC. Spread in masses and ages. Sample biased toward low v sini

16. One must not assume  log (N/H) = f(v sini) But  log (N/H) = f(v sini, M, age, Z….) Mass effectAge effect beginning of MS phase end of MS phase

18. MS stars between 14 and 20 M O in the list by Hunter et al. 2008 Gr I disappeared, except binaries lower M (~12 M O instead of 17 M O ) Gr II : evolved stars It would be useful to account for gravity darkening in v sin i to separate gravity effects due to rot. and evolution in M determinations

19. Galaxy: [N/H] for O-stars : ~ 0.5 up to 0.8-1.0 dex < 20 M  B – dwarfs : ~ 0.5 dex > 20 M  B – giants, supg. : ~0.5 -0.7 dex Ref: Villamariz & Herrero ’02; Smartt ’02;Herrero’03;Venn & Przybilla03;Trundle et al.’07 LMC: [N/H] for B-supg. : ~ 0.3 - 0.8 dex < 20 M  B – dwarfs : ~ 0.7- 0.9 dex B – giants, supg. :  1.1 -1.2 dex > 20 M  B – giants, supg. :  1.3 dex Ref: Herrero’03;Trundle et al. ’07;Hunter et al.’07 SMC: [N/H] O-stars, A-F supg. : 1.5 -1.7 dex < 20 M  B – dwarfs :  1.1 dex B – giants, supg. :  1.5 dex > 20 M  B – giants, supg :  1.9 dex Ref: Heap & Lanz’06; Venn & Przybilla’03; Bouret et al.’03;Trundle et al.’07; Hunter et al.’07 ABUNDANCES:

20. Gradients of  steeper at lower metallicity 20 M O More efficient mixing of the chemical elements at lower Z MM’ 01

21. 60 M sol, Z = 0.00001 2/3 of the Main Sequence phase spent near the break-up limit

22. Age in Myr 300 km/s 800 km/s MASS LOSS DUE TO THE APPROACH OF THE BREAK-UP LIMIT End MS Z=10 -8 Solar Z  radiative M - loss Low Z stars  rotational M-loss !

23. 14 N 12 C 16 O Y c = 0.40 Z surf /Z ini =1 Y c = 0.12 Z surf /Z ini =64 Y c = 0.08 Y c = 0.02 Z surf /Z ini =392Z surf /Z ini =1336 Z=10 -8

24. Also, ΔY/ΔZ > 70, cf.  Cen Maeder & Meynet 2006 ΔY/ΔZ= 70-130

25. Continuous line: models at Z=10 -5 (MM02) Broken line: the same with larger N yield Red: new models with fast rotation below Z=10 -5 Chiappini, Hirschi, Meynet, Ekström, Maeder., Matteucci 2006 Confirmed by Fabbian, Nissen, Asplund, Pettini, Ackerman 2008 Most extreme stars

26. Gamma-Ray Bursts (GRBs) Massive star collapsing in a fast spinning BH Composition: from SNIbc (WC-WO stars) Rotation: J > 10 16 cm 2 s -1 Statistics: ~1 GRB /1000 SN more at lower Z (up to SMC) Le Floch et al. 2003;Stanek et al. 2006 Collapsar model (Woosley 1993) Georgy et al. 2008

27. Yoon & Langer 2005; cf. Maeder, 1987 GRBs Difficulty: remove M without loosing too much angular momentum  homogeneous evolution - Homogeneous evolution. Possible, but composition not corresponding ! Avoid the red MM 2006

28. Anisotropic winds keep high rotation more M loss Meynet & Maeder 2006 0 2 4 (10 6 yr) Angular momentum in the central 3 M O = 8 x 10 16 cm 2 s -1 while j= 10 16 cm 2 s -1 is the limit.

29. Evolution of All Stellar Generations = f (M, Z, He, mass loss, rotation, binaries, magn. field, ……) Lifetimes, tracks Asteroseismology Evolution properties Be, B[e], LBV, WR stars in galaxies Nebulae Evolution of rotation Cepheid properties Surface abundances in massive stars and red giants Primary N Pre – supernova stages Yields and nucleosynthesis Rotation periods of pulsars Final masses Collapsars, γ- bursts, ….