Astronomy and Astrophysics – Astrophysics
Scientific paper
Mar 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001aipc..556..132h&link_type=abstract
EXPLOSIVE PHENOMENA IN ASTROPHYSICAL COMPACT OBJECTS: First KIAS Astrophysics Workshop. AIP Conference Proceedings, Volume 556,
Astronomy and Astrophysics
Astrophysics
Supernovae, Stellar Structure, Interiors, Evolution, Nucleosynthesis, Ages, Faint Blue Stars, White Dwarfs, Degenerate Stars, Nuclei Of Planetary Nebulae, Observational Cosmology
Scientific paper
Based on detailed models for the explosions, light curves and NLTE-spectra, evolutionary effects of Type Ia Supernovae (SNe Ia) with redshift have been studied to evaluate their size on cosmological time scales, how the effects can be recognized and how one may be able to correct for them. In the first part, we summarize the current status of scenarios for Type Ia Supernovae, including the explosion of a Chandrasekhar mass white dwarf (MCh-WD), the merging scenario and the helium-triggered explosions of low-mass WDs. We show that delayed detonation models can account for the majority of observations of spectra and light curves. IR observations are a new and powerful tools to constrain explosion models and details of the flame propagation in the WD. A strong Mg II line at 1.05 μm shows that nuclear burning takes place at the outer, low density layers. This requires a transition from the deflagration to the detonation regime of the nuclear burning front, or a very fast deflagration close to the speed of sound. We put the models into context with the empirical brightness decline relation which is widely applied to use SNe Ia as yardsticks on cosmological distance scales. This relation can be well understood in the framework of MCh-WDs as a consequence of the opacity effects in combination with the amount of 56Ni which determines the brightness. However, the amount of 56Ni actually produced depends on a combination of free parameters such as central density and the chemical composition of the WD, and the propagation of the burning front. We get a spread of ~0.4m around the mean relation which is larger than currently favored by observations (~0.12m, [40]) which may hint of an underlying coupling of the progenitor, the accretion rates and the propagation of the burning front. In a second part, we investigate the possible evolutionary effects in SNe Ia both with respect to changes in the sample of SNe Ia and individual variations, and how they can be identified. We find that evolution may produce an offset in the brightness decline relation is restricted to a few tenth of a magnitude. The effects reveal themself by changes in the U and UV fluxes, and in a change in the maximum brightness/decline relation by ΔM~0.1×Δt where Δt is the difference between local and distant SN-samples. According to new data [1], Δt<=1d and, thus, evolution is unlikely to eliminate a need for Λ. .
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