Issue |
A&A
Volume 425, Number 3, October III 2004
|
|
---|---|---|
Page(s) | 1029 - 1040 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20041108 | |
Published online | 28 September 2004 |
Nucleosynthesis in multi-dimensional SN Ia explosions*
1
Max-Planck Institut für Astrophysik, Karl-Schwarzschild Strasse 1, 85741 Garching bei München, Germany
2
Istituto Nazionale di Astrofisica (INAF) – Osservatorio Astronomico di Torino, via Osservatorio 20, 10025 Pino Torinese (Torino), Italy e-mail: travaglio@to.astro.it
3
Max-Planck Institut für Astrophysik, Karl-Schwarzschild Strasse 1, 85741 Garching bei München, Germany e-mail: wfh@mpa-garching.mpg.de
4
Max-Planck Institut für Astrophysik, Karl-Schwarzschild Strasse 1, 85741 Garching bei München, Germany e-mail: martin@mpa-garching.mpg.de
5
Department of Physics and Astronomy, University of Basel, Klingelbergstrasse B2, 4056 Basel, Switzerland e-mail: fkt@quasar.physik.unibas.ch
Received:
16
April
2004
Accepted:
11
June
2004
We present the results of nucleosynthesis calculations based on
multi-dimensional (2D and 3D) hydrodynamical simulations of the
thermonuclear burning phase in type Ia supernovae (hereafter
SN Ia). The detailed nucleosynthetic yields of our explosion models are
calculated by post-processing the ejecta, using passively advected
tracer particles. The nuclear reaction network employed in computing
the explosive nucleosynthesis contains 383 nuclear species, ranging
from neutrons, protons, and α-particles to 98Mo. Our models
follow the common assumption that SN Ia are the explosions of white
dwarfs that have approached the Chandrasekhar mass
(), and are disrupted by thermonuclear fusion of carbon and oxygen.
But in contrast to 1D models which adjust the burning speed to
reproduce lightcurves and spectra, the thermonuclear burning model
applied in this paper does not contain adjustable
parameters. Therefore variations of the explosion energies and
nucleosynthesis yields are dependent on changes of the initial
conditions only. Here we discuss the nucleosynthetic yields obtained in 2D
and 3D models with two different choices of ignition conditions
(centrally ignited, in which the spherical initial flame geometry is
perturbated with toroidal rings, and bubbles, in which
multi-point ignition conditions are simulated), but keeping the
initial composition of the white dwarf unchanged. Constraints imposed on the
hydrodynamical models from nucleosynthesis as well as from
the radial velocity distribution of the elements are discussed in
detail. We show that in our simulations unburned C and O
varies typically from ~40% to ~50% of the total ejected
material. Some of the unburned material remains between the flame
plumes and is concentrated in low
velocity regions at the end of the simulations. This effect is more
pronounced in 2D than in 3D and in models with a small number of
(large) ignition spots. The main differences between all our models and
standard 1D computations are, besides the higher mass fraction of
unburned C and O, the C/O ratio (in our case is typically a factor of
2.5 higher than in 1D computations), and somewhat lower abundances of certain
intermediate mass nuclei such as S, Cl, Ar, K, and Ca, and of 56Ni.
We also demonstrate that the amount of 56Ni produced in the explosion
is a very sensitive function of density and temperature. Because
explosive C and O burning may produce the iron-group
elements and their isotopes in rather different proportions
one can get different 56Ni-fractions (and thus supernova
luminosities) without changing the kinetic energy of the explosion.
Finally, we show that we need the high resolution multi-point ignition (bubbles)
model to burn most of the material in the center (demonstrating that high
resolution coupled with a large number of ignition spots is crucial to get rid of
unburned material in a pure deflagration SN Ia model).
Key words: hydrodynamics / nuclear reactions, nucleosynthesis, abundances / stars: supernovae: general
© ESO, 2004
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