Type Ia supernovae = thermonuclear explosions · 2007-05-03 · Type Ia supernovae = thermonuclear...
Transcript of Type Ia supernovae = thermonuclear explosions · 2007-05-03 · Type Ia supernovae = thermonuclear...
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Type Ia supernovae = thermonuclear explosions
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Homogeous spectra
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Exceptions
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Bump in IR
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Delta m15
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Stretch factorDelta m15MCLC
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Philips relation
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Hubble diagram
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Type Ia progenitors
I. Double degenerate = merging binary white dwars
II. Single degenerate = white dwarf + MS or red giant
Only one progenitor known = Tycho
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Explosion mechanism
Thermonuclear burning of C/O white dwarf as M > MChandra
Burning to NSE = 56Ni
I. Deflagration = subsonic burning front. WD expands ⇒ density decreases ⇒ only center to NSE ⇒ C, O, Mg, Si, Ca on outside
II. Detonation = supersonic burning front. WD does not have time to expand ⇒ whole star to NSE ⇒ 56Ni only
Observations: Lines of Si, Mg, ... at high velocity
No C/O at low velocity
Delayed detonation
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Delayed det.
Deflagration
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Riess et al 2006
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Systematic effects?1. Dust extinction. Use IR and elliptical galaxies
2. Evolutionary effects: C/O ratio depends on metallicity. Explosion energy depends on C or O.
3. Different progenitors? Some in star forming galaxies, some in ellipticals.
4. Contamination by Type Ib/c SNe
No strong indications of evolutionary effects are found
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Hubble diagram in IR
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Conclusions
1. We do not know the progenitors
2. We do not understand the explosion mechanism
3. Type Ias are still good standard candles