ROTATING MASSIVE STAR MODELS: FROM PRIMORDIAL STARS TO HIGH METALLICITY REGIONS - PowerPoint PPT Presentation

slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
ROTATING MASSIVE STAR MODELS: FROM PRIMORDIAL STARS TO HIGH METALLICITY REGIONS PowerPoint Presentation
Download Presentation
ROTATING MASSIVE STAR MODELS: FROM PRIMORDIAL STARS TO HIGH METALLICITY REGIONS

play fullscreen
1 / 81
ROTATING MASSIVE STAR MODELS: FROM PRIMORDIAL STARS TO HIGH METALLICITY REGIONS
165 Views
Download Presentation
kalli
Download Presentation

ROTATING MASSIVE STAR MODELS: FROM PRIMORDIAL STARS TO HIGH METALLICITY REGIONS

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. ROTATING MASSIVE STAR MODELS: FROM PRIMORDIAL STARS TO HIGH METALLICITY REGIONS Georges Meynet, André Maeder, Raphael Hirschi and Sylvia Ekstroem Geneva Observatory

  2. Ionising sources, energy and momentum sources, nucleosynthetic sites Effects of SN in a galaxy: GALACTIC WINDS Filaments from Supernovae

  3. ROTATION… An old topic… Von Zeipel 1924; Eddington 1925; Vogt 1925

  4. … but quite topical nowadays Star deformation due to its fast axial rotation Dominiciano de Souza et al. 2003 Cf also van Belle et al. 2003 Link between Long GRB and Hypernova confirmed Hjorth et al. 2003

  5. O-type stars in the SMC Nine of 17 O-type stars show a surface enrichment of N up to a solar level, [N]=7.92. Heap and Lanz 2003; 2005

  6. PHYSICS OF ROTATION • STRUCTURE • Oblateness (interior, surface) • New structure equations • Shellular rotation • MIXING • Meridional circulation • Shear instabilities + diffusion • Horizontal turbulence • Advection + diffusion of • angular momentum • Transport + diffusion of the • chemical elements • MASS LOSS • Increase of mass loss by rotation • Anisotropic losses of angular • momentum

  7. Cells of meridional circulation Very important process for the transport of the angular momentum 20 Msol on the ZAMS Outwards and inwards transport of angular momentum GRATTON- ÖPIK CELL Occurs when star deformed…

  8. Meridional circulation Gradients of Shear instabilities Zahn 1992: strong horizontal turbulence, shellular rotation Transport of the chemical species Transport of the angular momentum

  9. … the radiation observed to be emitted must work its way through the star, and if there were too much obstruction it would blow up the star. » «

  10. Frad geff The Von Zeipel theorem (1924)

  11. STELLAR WINDS & ROTATION Maeder, 1999 ; cf. Owocki, 1996 iso mass loss For stellar formation also

  12. Idem with Teff =25000 K

  13. van Boekel et al. 2003

  14. New grids of stellar models Also Z=0.040; 0.008, 0.004, 0.00001 +Pop III Meynet and Maeder 2003

  15. N/C growsduring the MS, even for early B stars (cf.Lyubimkov 1996) OK with B, A supergiants (cf. Gies & Lambert 1992; Lennon 1994; Venn 1998,…) (cf. Maeder, 1987; Langer, 1992; ….) 300 km/s 200

  16. Gradients of  steeper at lower metallicity 20 Msol, Xc mass fraction of H at the centre, Vini= 300 km/s Stars more compact, transport of angular momentum less efficient Why ? Consequences ? More efficient mixing of the chemical elements

  17. 9 Msol When Z Surface enrichments

  18. Number of stars Max/ini N/H =40 Log (N/H)+12 6.4 6.8 7.2 7.6 8.0 8.4 8.8 Max/ini N/H =8 Venn & Przybilla 2003

  19. B/R PROBLEM Lots of RSG observed at low Z, but current models predict none. B/R ~ 50 Langer & Maeder, 1995 Models with rotation are OK with B/R = 0.5–0.8 in SMC cf. Maeder & Meynet 2001

  20. NUMBER RATIOS OF MASSIVE STARSIN NEARBY GALAXIES GALAXY Z WR/O WC/WR RSG/WR Conti & Maeder’94; Massey ‘02

  21. 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

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

  23. Meynet and Maeder 2004 Observed points from Prantzos and Boissier (2003)

  24. 25 Msol: from core H-burning to Si-burning V=0 km/s V=300 km/s Hirschi, Meynet, Maeder, 2004 Heger, Langer, Woosley 2000

  25. PRIMARY NITROGEN HII regions Pagel 1997 Garnett 1990 Metal-poor dwarfs of the Solar neighborhood DLA Pettini et al 2002 Carbon et al. 1987

  26. A new mechanism induced by rotation S-process ? Cf. Herwig et al, 2003

  27. For Z=0.004 and Z=0.020 , nearly no primary N production

  28. At Z= 0, stars are more compact PopIII star: radii decreased by a factor 4 DELTA Log Teff~0.3 Feijoo 1999 diploma work Ekström 2004 diploma work

  29. 16O 4He 16O 4He 1H 1H 12C 12C 14N 60 Msol 25Msol ~30Msol Pop III 14N Mco larger in the rotating model Chemical composition of the radiative envelope PRIMARY 13C and 14N

  30. CONSEQUENCES FOR NUCLEOSYNTHESIS Z = 0 rotating Z = 0.00001 -6.6 Non rotating

  31. New data 2004 Spite et al. 2004 Israelian et al. 2004 NEED OF IMPORTANT PRIMARY PRODUCTION BY MASSIVE STARS

  32. Mass loss rates much lower Cf Kudritzki, Hillier MIGHT THE STAR LOOSE MASS BY OTHER PROCESSES ? Vini=300 km/s NO MASS LOSS Mass loss rates from Vink et al. 2000;2001 FINAL MASS Meynet and Maeder 2004 INITIAL MASS

  33. Vsurf Z= 0.020 Z= 0.004 Vini on the ZAMS = 300 km/s Age [in My] Z= 0.00001

  34. Pop III stellar models 40Msol 60Msol 85 Msol 200 Msol Mass Fraction of Hydrogen at the centre

  35. 60 Msol, [Fe/H]=-3.3 and –6.3 Non rotating Log Teff Rotating Yc

  36. 4He 4He 14N Yc= 0.12 12C Zsurf/Zini=64 Yc= 0.40 Zsurf/Zini=1 16O 4He 4He [Fe/H]=-3.3 Yc= 0.08 Zsurf/Zini=392 Case for [Fe/H]=-6.3 Very similar Yc= 0.02 Zsurf/Zini=1336

  37. COMPOSITION OF THE WIND EJECTA

  38. Evolution = f (M, Z, Ω, …)

  39. ROTATING MODELS Surface enrichements Blue to red supergiants ratio at low metallicity Wolf-Rayet to O-type stars at various metallicities Type Ibc to type IIsupernovae at various metallicities At low metallicity predict higher enrichments higher velocities primary Nitrogen very metal poor stars Pulsar rotation rates/GRB progenitors

  40. 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 ?

  41. Do the models reproduce the observed rotation rate of young pulsars ? Observed rotation periods of young pulsars: 2ms – 100 ms (20ms) Middletich et al. 2000; Romani & Ng 2003; Marshall et al. 2003 Pre SN 25 – 320 X angular momentum in young pulsars In pre SN stages, more efficient angular momentum Processes ? For NS with P=20ms Loss of angular momentum during the collapse ? Fryer and Warren 2004

  42. Relation SN - GRB COLLAPSAR: Woosley, 2002 Hjorth et al. 2003 Precursor: Rotating WR star ? Is there enough rotation ? 1 % of all WR would be enough.

  43. Conditions for a collapsar WR To have sufficient angular momentum Pre SN Zsol  > 1016 cm2 s-1 But No WO STARS ! For NS at break-up Woosley 2003 To have lost its H-rich envelope, to be a WO star (Mhe > 8 Msol-> BH) For NS with P=20mms

  44. WR Zsol ZSMC Candidates for Collapsars, reduced region at low Z

  45. WR At Z=0.004 ~1% of the Core collapse supernovae are of type Ic Zsol ZSMC WO Candidates for Collapsars, reduced region at low Z

  46. Conclusions: Evolution = f (M, Z, Ω) • Evolution of rotational velocities • Lifetimes, tracks • Evolution properties Be, B[e], LBV, • WR stars in galaxies • Nebulae • Cepheid properties • Surface abundances in massive stars • and red giants • Primary N • Pre – supernova stages • Chemical yields and nucleosynthesis • Rotation periods of pulsars • Final masses • Collapsars, γ- bursts, ….

  47. A correct treatment of the transport of angular momentum in all phases is necessary ! If so, high final ang. momentum Hirschi, Meynet & Maeder, 2004