Supernovae of type Ia: the final fate of low mass stars in close bynary systems Oscar Straniero INAF – Oss. Astr. di Collurania (TE)

CMB Temperature fluctuations (COBE BOOMERANG WMAP)

 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

Standard Model =  CDM model CMB + SNe + H 0

SNe + CMB SNe: Perlmutter et al. 1998, Riess et al " 1 Gyr (H o =63) SNe+WMAP+HST 13.2 " 0.4 Gyr (H o =71) Spergel et al " 0.2 Gyr

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

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 

Observed Relations Riess et al., 1997 Brighter Slower Decline Dimmer Faster Decline

Calibrated locally Phillips et al. 1996, 1999 = 0.17 mag Maximum Brightness - Decline Relation

Do Supernovae change with z ?? Hamuy et al., 2000 Ivanov et al  SN Ia rate is smaller in Ellipticals Cappellaro et al  SN Ia LCs Slower (brighter) in Bluer Galaxies Hamuy et al., 1995, 1996 Branch et al Hints... Back in time>>Progenitors Younger & more metal-poor

…… 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.

log  log P  5/3  4/3 M1M1 M2M2 Non-degenerate Non-relativistic relativistic collapse The virial theorem

Massive stars and core collapse e - +p  n+ e (10 MeV) 56 Fe+   13  +4n (124 MeV) Limongi, Straniero & Chieffi, 2001

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

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 = M  ONeMg WD .  1-10 Myr M f = M  Fe (Y e. 0.45) collapse NS or BH  #1  Myr O (pair jnstability) (Y e =0.5) may or may not explode

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

Nucleosynthesis in Thermonuclear SNe He-detonation C-delayed detonation C-deflagration

SNe Ia Light Curves: mass and metallicity effects Domínguez, Hoflich, Straniero 2001

Most of the accreted material is lost during the H-pulse: too long time H accreting WDs RG MS

Merging scenario: Double degenerate systems: CO+CO a) GWR loss b) secondary tidal disruption c) accretion M  yr -1 Too fast accretion

(M=8 H M  yr -1 ) Double Degenerate CO WDs (M=10 -8 M  yr -1 )

Single Degenerate. Massive WDs: the lifting effect of rotation H He CO Dominguez, Straniero, Isern & Tornambe’ 1996

Double Degenerate Angular momentum deposition & GWR c) accretion 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

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

The future