zorro and the nature of sne ia
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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. - PowerPoint PPT PresentationTRANSCRIPT
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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
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Obs.Rel.1: The Phillips Relation (Absolute Magnitude - Decline Rate)
Phillips 1992
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O.R. 2: Bolometric Light Curves
Contardo et al. 2000
Lpeak - decline rate or LC shape
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SNe Ia @ maximum
“Branch normals”
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SNe Ia @ 20 days after maximum
“Branch normals”
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SNe Ia: late-time spectra
Mazzali et al. 1998
Δm15(B)
1.93
1.77
1.27
1.51
0.87
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O.R.3: Nebular line width - decline rate
after Mazzali et al. 1998
56Ni mass and distribution and decline rate (≡Luminosity) are related
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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
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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)
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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
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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
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Need a few blobs or a thick torus
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Use blobs to fit spectra
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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
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Modelling late-time spectra
Full view of inner ejecta (56Ni zone)
Monte Carlo LC code + NLTE nebular code
• No radiative transfer• Estimate masses
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Result: Composition in a typical SN Ia
• SN 2002bo
m15(B)=1.15
(average)
• Elements more mixed than in typical 1D models
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Test: Modelling Light Curve
Monte Carlo code• Use W7 density• Composition from
tomography
• 56Ni ~0.50M Model LC matches
data very well
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IV. The Global View
• Late time spectra suggest M(56Ni) Δm15(B) [ M(Bol)] v(Fe)
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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) and Δm15(B)
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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.
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Putting it all together: “ orro” diagramA basic property of SNe Ia
Mass burned ~ constant
Progenitor mass also probably constant: MCh
KE ~ const
What does it all mean?• Delayed detonation?• Multi-spot ignited deflagration?• Other possibilities….?
Stable 54Fe, 58Ni
56Ni
IME
Mazzali et al. (2006), Science
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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
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V. Explaining the Phillips’ Relation
Models with increasing 56Ni content reproduce Phillips’ Relation
(Mazzali et al. 2001)
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Spectra also reproduced
Mazzali et al. 2001
-7days Max
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Using Zorro to reconstruct Phillips’ Rel’n
• Use composition to compute LC parameters
•
•
•
•
• Derive Phillips Relation
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Using Zorro to reconstruct Phillips’ Rel’n
• Use composition to compute LC parameters • Derive Phillips Relation
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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)
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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