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Supernovae of type Ia: the final fate of low mass stars in close bynary systems Oscar Straniero INAF – Oss. Astr. di Collurania (TE)
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CMB Temperature fluctuations (COBE BOOMERANG WMAP)
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Supernova Cosmology Project High-z Team (Brian Schmidt & co) The Universe is Accelerating: 0.25 mag fainter than for an EMPTY Universe (Saul Perlmutter & co.) Fainter = Further
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Standard Model = CDM model CMB + SNe + H 0
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SNe + CMB SNe: Perlmutter et al. 1998, Riess et al. 1998 14.5 " 1 Gyr (H o =63) SNe+WMAP+HST 13.2 " 0.4 Gyr (H o =71) Spergel et al. 2003 13.7 " 0.2 Gyr
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SNe Classification Core collapse of massive stars Thermonuclear explosion I b (strong He) I c (weak He) SNe II p Type II II L No H H Type I I a (strong Si) based on spectra and light curve morphology
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Standard Candles Bright Homogeneous No evolutionary effects Supernovae Ia Light Curve L time 56 Ni 56 Co 56 Fe Thermonuclear Explosion of a CO WD M~M Chandrasekhar L M Ni ~ 1.4 M
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Observed Relations Riess et al., 1997 Brighter Slower Decline Dimmer Faster Decline
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Calibrated locally Phillips et al. 1996, 1999 = 0.17 mag Maximum Brightness - Decline Relation
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Do Supernovae change with z ?? Hamuy et al., 2000 Ivanov et al. 2000 SN Ia rate is smaller in Ellipticals Cappellaro et al. 1997 SN Ia LCs Slower (brighter) in Bluer Galaxies Hamuy et al., 1995, 1996 Branch et al. 1996 Hints... Back in time>>Progenitors Younger & more metal-poor
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…… bombs often fail. Similarly, most models for astrophysical bombs (Sne Ia) often fail. The conceptually simplest model for a thermonuclear supernova is just an analog of a runaway chemical reaction that become explosive : a conventional bomb. …… Further, astrophysical bombs must occur naturally and at the correct rate: there must be a convincing astronomical context.
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log log P 5/3 4/3 M1M1 M2M2 Non-degenerate Non-relativistic relativistic collapse The virial theorem
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Massive stars and core collapse e - +p n+ e (10 MeV) 56 Fe+ 13 +4n (124 MeV) Limongi, Straniero & Chieffi, 2001
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Evolutionary track of low mass stars 0.6 CO 0.55 He 0.2 CO 0.1 He 0.5 He 0.6 CO WD MS RGBHB AGB PN M=1 M u =10 Gyr Remnant: CO WD 0.6 M u Prada Moroni & Straniero 2002
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Stellar evolution M<0.8 M 0.8<M/M <8 8<M/M <11 11<M/M <100 M>100 M Gyr Myr 0.5<M f /M <1.1 CO WD . Myr M f =1.2-1.3 M ONeMg WD . 1-10 Myr M f =1.2-2.5 M Fe (Y e. 0.45) collapse NS or BH #1 Myr O (pair jnstability) (Y e =0.5) may or may not explode
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Astrophysical Explosive Devices Gravitational collapse Induced Core collapse (nuclear runaway fails) Pair instability, core collapse & O explosion (core collapse fails) C-deflagration C or He detonation C-delayed detonation Thermonuclear SNe RG WD
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Nucleosynthesis in Thermonuclear SNe He-detonation C-delayed detonation C-deflagration
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SNe Ia Light Curves: mass and metallicity effects Domínguez, Hoflich, Straniero 2001
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Most of the accreted material is lost during the H-pulse: too long time H accreting WDs RG MS
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Merging scenario: Double degenerate systems: CO+CO a) GWR loss b) secondary tidal disruption c) accretion 10 -5 M yr -1 Too fast accretion
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(M=8 H 10 -6 M yr -1 ) Double Degenerate CO WDs (M=10 -8 M yr -1 )
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Single Degenerate. Massive WDs: the lifting effect of rotation H He CO Dominguez, Straniero, Isern & Tornambe’ 1996
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Double Degenerate Angular momentum deposition & GWR c) accretion 10 -5 M yr -1 (expansion) d) “critical” accretion (contraction) e) tri-axial configuration and energy loss via GWR f) balance between ang. mom. deposition and energy loss (steady accretion) g) Viscous dissipation and explosion d c e f g ---- disk ---- WD Piersanti, Gagliardi, Iben & Tornambe’ 2003
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Open Problems: Progenitors ?? Accretion, Rotation. Propagation of the burning front (1D/3D) ?? Transition density How stellar populations evolve with z ?? Our main results for SNe Ia: Up to M MAX =0.2 mag C/O WDs due to different M MS correlated with v ph & t rise No dependence of M MAX with initial Z
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The future
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