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
Jan 22, 2016
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