Discussions about Z effects on the Conti scenario
Discussions about Z effects on the Conti scenario Geneva, 1983
Peter sitting on pure Z=1 materials in Arapahoe Peak Boulder, 1989
Peter during a bicycle trip Geneva 2002
Peter with some of his many disciples… Boulder, 2003
MASSIVE STARS EVOLUTION in collaboration with : Georges Meynet Raphael Hirschi (Univ. Keele) Patrick Eggenberger (Univ. Liege) Sylvia Ekström Cyril Georgi
MASSIVE STARS: High T Low MASS LOSS : MIXING: shear ~ thermal diffusivity Mass loss and mixing strongly favoured !
Both effects interact: - Mass loss removes angular momentum - Rotation enhances the M- loss rates Rotation in B stars Huang & Gies (2006); see also Conti & Ebbets 1977 - Peak of Vrot = 200 km/s • STRUCTURE Oblateness • MASS LOSS Enhanced winds Anisotropies • MIXING Meridional circul. Shears Hzt. turbulence
ROTATIONAL DISTORTION ACHERNAR ~9. 6 Msol Domiciano de Souza et al. 2003 : difficulty ? Carciofi et al. 2008: equatorial disk Re/Rp=1. 5 ROCHE MODEL OK for ω =0. 992
Von Zeipel (1924) Frad geff Teff ~ geff 1/4
GRAVITY DARKENING Altair 1. 8 Msol ω =0. 9 Teff(pole)/Teff(equateur)=1. 23 -1. 27 Confirmation of Von Zeipel Peterson et al. 2006 Monnier et al. 2007 The exponent may be smaller ~0. 19 Monnier, 2007
STELLAR WINDS & ROTATION Owocki 1996, Maeder, 1999 Enables a massive star to lose lots of mass and little angular momentum GRBs iso mass loss
ACHERNAR HAS POLAR WINDS 9. 6 Msol Ve=470 km/s ~91% Vcrit Mass of the disk =4. 1 10 -10 Msol Mass loss =1. 3 10 -8 Msol/y Polar mass flux 7 10 -9 Msol y-1 sr-1 Disk in Keplerian rotation Meilland et al. 2007 Intensity map in the continuum at 2. 15 micron (SIMECA code)
(N/H) depend on - v sin i -M - age - Z, etc… SURFACE ENRICHMENTS
Stars in extended regions around N 11 and NGC 2004 in the LMC. Spread in masses and ages. Sample biased toward low v sini « The observation challenges the concept of rotational mixing » Hunter et al. 2008
log (N/H) = f(v sini) log (N/H) = f(v sini, M, age, Z…. ) One must not assume But Age effect en do f. M Sp ha se Mass effect beginning of MS phase
MS stars between 14 and 20 MO in the list by Hunter et al. 2008 Gr I disappeared, except binaries lower M (~12 MO instead of 17 MO) 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
![ABUNDANCES: Galaxy: [N/H] for O-stars : ~ 0. 5 up to 0. 8 -1.](http://slidetodoc.com/presentation_image_h/1409053311c5de9100dfbf1b17417041/image-19.jpg "ABUNDANCES: Galaxy: [N/H] for O-stars : ~ 0. 5 up to 0. 8 -1.")
ABUNDANCES: 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 & Przybilla 03; 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
Gradients of steeper at lower metallicity 20 MO More efficient mixing of the chemical elements at lower Z MM’ 01
60 Msol, Z = 0. 00001 2/3 of the Main Sequence phase spent near the break-up limit
MASS LOSS DUE TO THE APPROACH OF THE BREAK-UP LIMIT Z=10 -8 300 km/s End MS 800 km/s Solar Z radiative M - loss Low Z stars rotational M-loss Age in Myr !
Zsurf/Zini=1 Zsurf/Zini=64 14 N Yc= 0. 12 12 C Yc= 0. 40 16 O Zsurf/Zini=392 Zsurf/Zini=1336 Yc= 0. 08 Z=10 -8 Yc= 0. 02
ΔY/ΔZ= 70 -130 Also, ΔY/ΔZ > 70, cf. Cen Maeder & Meynet 2006
Most extreme stars Continuous line: models at Z=10 -5 (MM 02) 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
Gamma-Ray Bursts (GRBs) Collapsar model (Woosley 1993) Massive star collapsing in a fast spinning BH • Composition: from SNIbc (WC-WO stars) • Rotation: J > 1016 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 Georgy et al. 2008
GRBs Difficulty: remove M without loosing too much angular momentum homogeneous evolution Avoid the red Yoon & Langer 2005; cf. Maeder, 1987 MM 2006 - Homogeneous evolution. Possible, but composition not corresponding !
0 2 4 (106 yr) Anisotropic winds • keep high rotation • more M loss Meynet & Maeder 2006 Angular momentum in the central 3 MO = 8 x 1016 cm 2 s-1 while j= 1016 cm 2 s-1 is the limit.
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, ….
- Slides: 30
