The role of electron captures in Chandrasekhar-mass models for Type Ia supernovae

Citation
F. Brachwitz et al., The role of electron captures in Chandrasekhar-mass models for Type Ia supernovae, ASTROPHYS J, 536(2), 2000, pp. 934-947
Citations number
61
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Space Sciences
Journal title
ASTROPHYSICAL JOURNAL
ISSN journal
0004-637X → ACNP
Volume
536
Issue
2
Year of publication
2000
Part
1
Pages
934 - 947
Database
ISI
SICI code
0004-637X(20000620)536:2<934:TROECI>2.0.ZU;2-8
Abstract
The Chandrasekhar-mass model for Type Ia supernovae (SNe Ia) has received i ncreasing support from recent comparisons of observations with light-curve predictions and modeling of synthetic spectra. It explains SN Ia events via thermonuclear explosions of accreting white dwarfs in binary stellar syste ms, being caused by central carbon ignition when the white dwarf approaches the Chandrasekhar mass. As the electron gas in white dwarfs is degenerate, characterized by high Fermi energies for the high-density regions in the c enter, electron capture on intermediate-mass and Fe group nuclei plays an i mportant role in explosive burning. Electron capture affects the central el ectron fraction Y-e, which determines the composition of the ejecta from su ch explosions. Up to the present, astrophysical tabulations based on shell model matrix elements were available only for light nuclei in the sd-shell. Recently, new shell model Monte Carlo and large-scale shell model diagonal ization calculations have also been performed for pf-shell nuclei. These le ad in general to a reduction of electron capture rates in comparison with p revious, more phenomenological, approaches. Making use of these new shell m odel-based rates, we present the first results for the composition of Fe gr oup nuclei produced in the central regions of SNe Ia and possible changes i n the constraints on model parameters like ignition densities pi,, and burn ing front speeds v(def).