Type Ia Supernovae: standard candles? Roger Chevalier

Supernovae – spectroscopic classification Type I – H absent Type II – H present Filippenko 97

Light curves Filippenko 97

Late spectra Filippenko 97

Why SN Ia for cosmology? Luminous Luminous Can occur in older stellar population; not closely tied to star forming regions Can occur in older stellar population; not closely tied to star forming regions Uniform in properties Uniform in properties e.g., Colgate 79

Basic interpretation (c. 1980) Thermonuclear explosion of Chandrasekhar mass (1.4 M  ) white dwarf Thermonuclear explosion of Chandrasekhar mass (1.4 M  ) white dwarf Not a complete detonation Not a complete detonation No compact remnant No compact remnant The white dwarf accretes in a binary system The white dwarf accretes in a binary system The burning produces ~0.6 M  of 56 Ni, the decay of which powers the light curve The burning produces ~0.6 M  of 56 Ni, the decay of which powers the light curve

Nuclear fusion gives ~10 51 ergs Nuclear fusion gives ~10 51 ergs Adiabatic expansion in going from 10 9 cm to cm Adiabatic expansion in going from 10 9 cm to cm Power for radiation (~10 49 ergs) provided by radioactivity Power for radiation (~10 49 ergs) provided by radioactivity

Chevalier 81

Woosley & Weaver 86

Late spectrum

Phillip’s relation (1993)

Hamuy et al. 96 Filippenko 97

Application of the Phillip’s relation Hamuy et al. 96

Light Curve Shape method Reiss, Press, Kirshner 96

SCP (Supernova Cosmology Project) SCP (Supernova Cosmology Project) S. Perlmutter et al. S. Perlmutter et al. Used Phillip’s relation and light curve “stretch” Used Phillip’s relation and light curve “stretch” HZT (Hi – z Supernova Search Team) HZT (Hi – z Supernova Search Team) B. Schmidt et al. B. Schmidt et al. Used LCS method Used LCS method

Riess et al SN Ia Discoveries at z>1 from the HST

Spectra SN type Redshift z Riess et al.

Evolution leading to SN Ia Single degenerate in binary (standard model) Single degenerate in binary (standard model) Low accretion of H – explodes and blown off Low accretion of H – explodes and blown off dM/dt>10 -7 M  /yr, stable accretion dM/dt>10 -7 M  /yr, stable accretion dM/dt>3x10 -7 M  /yr, build up envelope → spiral-in? dM/dt>3x10 -7 M  /yr, build up envelope → spiral-in? “Hachisu” wind? “Hachisu” wind? Double degenerate Double degenerate Gravitational radiation drives binary evolution Gravitational radiation drives binary evolution But, unstable mass transfer → burning to ONe WD → accretion induced collapse But, unstable mass transfer → burning to ONe WD → accretion induced collapse

Explosion physics 1-dimensional (spherical) models 1-dimensional (spherical) models Deflagration Deflagration DD – delayed detonation DD – delayed detonation PDD – pulsating delayed detonation PDD – pulsating delayed detonation 3-dimensional models 3-dimensional models Importance of Rayleigh-Taylor instability Importance of Rayleigh-Taylor instability Ropke & Hillebrandt 05

Explaining the Phillips’ relation Metallicity – more CNO → more 22 Ne → less 56 Ni Central density at time of ignition Travaglio et al. 05

Conclusions We do not understand evolution leading to explosion, explosion mechanism, Phillips’ relation… We do not understand evolution leading to explosion, explosion mechanism, Phillips’ relation… But, there are no indications that the high-z SNe Ia are different from nearby ones But, there are no indications that the high-z SNe Ia are different from nearby ones