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Zorro and the nature of SNe Ia

Zorro and the nature of SNe Ia. Paolo A. Mazzali Max-Planck Institut f ü r Astrophysik, Garching Astronomy Department and RESearch Centre for the Early Universe, University of Tokyo Istituto Naz. di Astrofisica, OATs.

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Zorro and the nature of SNe Ia

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  1. Zorro and the nature of SNe Ia Paolo A. Mazzali Max-Planck Institut für Astrophysik, Garching Astronomy Department and RESearch Centre for the Early Universe, University of Tokyo Istituto Naz. di Astrofisica, OATs

  2. Obs.Rel.1: The Phillips Relation (Absolute Magnitude - Decline Rate) Phillips 1992 22.5.2008

  3. O.R. 2: Bolometric Light Curves Lpeak - decline rate or LC shape Contardo et al. 2000 22.5.2008

  4. SNe Ia @ maximum “Branch normals” 22.5.2008

  5. SNe Ia @ 20 days after maximum “Branch normals” 22.5.2008

  6. SNe Ia: late-time spectra Δm15(B) 1.93 1.77 1.27 1.51 0.87 Mazzali et al. 1998 22.5.2008

  7. O.R.3: Nebular line width - decline rate 56Ni mass and distribution and decline rate (≡Luminosity) are related after Mazzali et al. 1998 22.5.2008

  8. OR4: Velocity Gradients: an alternative SN Ia classification • Benetti et al. (2005): • Classify SNeIa according to rate of change of post-maximum photospheric velocity of SiII 6355 •  3 SN groups: High Velocity GradientLow Velocity GradientFaint • Groups separate out in v-ΔM15(B) plot 22.5.2008

  9. II. Outer regions of the ejecta: HVFs • Nearly all SNe show very High Velocity (~20000 km/s) absorption Features (HVF) in Ca II (some also in Si II) Mazzali et al (2005) 22.5.2008

  10. HVFs trace the outer explosion What makes the HVFs? • Abundance enhancement unlikely • Density enhancement more reasonable (incl. H) • Ejection of blobs or CSM interaction? • Blobs: line profiles depend on orientation 22.5.2008

  11. Distribution of HVFs • Any model should reproduce the observed distribution of HVF wavelength (blob velocity) and strength (optical depth, covering factor) • Single blob does not 22.5.2008

  12. Need a few blobs or a thick torus 22.5.2008

  13. Use blobs to fit spectra 22.5.2008

  14. III. Abundance Stratification • Model spectral sequence to derive composition layering: explore the depth of the star • How did the star burn? Stehle et al 2005 22.5.2008

  15. Modelling late-time spectra Full view of inner ejecta (56Ni zone) Monte Carlo LC code + NLTE nebular code • No radiative transfer • Estimate masses 22.5.2008

  16. Result: Composition in a typical SN Ia • SN 2002bo m15(B)=1.15 (average) • Elements more mixed than in typical 1D models 22.5.2008

  17. Test: Modelling Light Curve Monte Carlo code • Use W7 density • Composition from tomography • 56Ni ~0.50M  Model LC matches data very well 22.5.2008

  18. IV. The Global View • Late time spectra suggest M(56Ni)  Δm15(B) [ M(Bol)]  v(Fe) 22.5.2008

  19. Role of 54Fe, 58Ni • Stable Fe group isotopes radiate but do not heat • Some anticorrelation between 56Ni and (54Fe, 58Ni) • Very good correlation beween Σ(NSE)andΔm15(B) 22.5.2008

  20. Composition Layering • Outer extent of NSE zone varies ( Δm15(B), Lum) • Inner extent of IME matches outer extent of NSE • Outer extent of IME ~ const. 22.5.2008

  21. Putting it all together: “ orro” diagram A basic property of SNe Ia Mass burned ~ constant  Progenitor mass also probably constant: MCh • KE ~ const IME • What does it all mean? • Delayed detonation? • Multi-spot ignited deflagration? • Other possibilities….? 56Ni Stable 54Fe, 58Ni Mazzali et al. (2006), Science 22.5.2008

  22. The Role of Fe-group, IME on LC • 56Ni: light, opacity, KE • 54Fe, 58Ni: opacity, KE • IME: KE, some opacity • CO (if any): little opacity 22.5.2008

  23. V. Explaining the Phillips’ Relation Models with increasing 56Ni content reproduce Phillips’ Relation (Mazzali et al. 2001) 22.5.2008

  24. Spectra also reproduced -7days Max Mazzali et al. 2001 22.5.2008

  25. Using Zorro to reconstruct Phillips’ Rel’n • Use composition to compute LC parameters • Derive Phillips Relation 22.5.2008

  26. Using Zorro to reconstruct Phillips’ Rel’n • Use composition to compute LC parameters  • Derive Phillips Relation  22.5.2008

  27. Effect of stable NSE (54Fe, 58Ni) • Amount of 54Fe, 58Ni may be a fn. of WD metallicity (Timmes et al. 2003) • Ratio 56Ni/NSE affects light, not KE or opacity • LCs w/ different peak brightness, same decline rate • May cause spread about the Phillips’ Relation.(Mazzali & Podsiadlowski 2006) 22.5.2008

  28. Conclusions • There is some regularity among SNe Ia (surprise surprise…) • Ejecta reflect stratified composition of models • Total mass burned may be constant • 56Ni determines luminosity (not new) • Total NSE determines LC shape • Degree of neutronization can give rise to dispersion in luminosity-decline rate relation • Z evolution may confuse cosmological parameters 22.5.2008

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