Issue |
A&A
Volume 453, Number 2, July II 2006
|
|
---|---|---|
Page(s) | 661 - 678 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20054512 | |
Published online | 16 June 2006 |
Non-spherical core collapse supernovae
II. The late-time evolution of globally anisotropic neutrino-driven explosions and their implications for SN 1987 A
1
Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Straße 1, 85741 Garching, Germany e-mail: kok@mpa-garching.mpg.de
2
Center for Astrophysical Thermonuclear Flashes, University of Chicago, 5640 S. Ellis Avenue, Chicago, IL 60637, USA
Received:
12
November
2005
Accepted:
20
February
2006
Two-dimensional simulations of strongly anisotropic
supernova explosions of a nonrotating blue
supergiant progenitor are presented, which follow the
hydrodynamic evolution from times shortly after shock
formation until hours later. It is shown that explosions
which around the time of shock revival are dominated by
low-order unstable modes (i.e. by a superposition of the
and
modes, in which the former is strongest),
are consistent with all major observational features of SN
1987 A, in contrast to models which show high-order mode
perturbations only and were published in earlier work. Among
other items, the low-mode models exhibit final iron-group
velocities of up to
km s-1, strong mixing at the
He/H composition interface, with hydrogen being mixed
downward in velocity space to only 500 km s-1, and a final
prolate anisotropy of the inner ejecta with a major to minor
axis ratio of about 1.6. The success of low-mode explosions
with an energy of about
erg to reproduce
these observed features is based on two effects: the (by 40%) larger initial maximum velocities of metal-rich clumps
compared to our high-mode models, and the initial global
deformation of the shock. The first effect protects the
(fastest) clumps from interacting with the strong reverse
shock that forms below the He/H composition interface, by
keeping their propagation timescale through the He-core
shorter than the reverse shock formation time. This ensures
that the outward motion of the clumps remains always
subsonic, and that thus their energy dissipation is minimal
(in contrast to the supersonic case). The second effect is
responsible for the strong inward mixing of hydrogen: the
aspherical shock deposits large amounts of vorticity into
the He/H interface layer at early times (around
s). This triggers the growth of a strong
Richtmyer-Meshkov instability that results in a global
anisotropy of the inner ejecta at late times (i.e. around
s), although the shock itself has long become
spherical by then. The simulations suggest a coherent
picture, which explains the observational data of SN 1987 A
within the framework of the neutrino-driven explosion
mechanism using a minimal set of assumptions. It is
therefore argued that other paradigms, which are based on
(more) controversial physics, may not be required to explain
this event.
Key words: hydrodynamics / instabilities / nucleosynthesis / shock waves / supernovae: general
© ESO, 2006
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