摘要：The gravitationally confined detonation (GCD) model has been proposed as a possible
explosion mechanism for Type Ia supernovae in the single-degenerate evolution channel. It
starts with ignition of a deflagration in a single off-centre bubble in a
near-Chandrasekhar-mass white dwarf. Driven by buoyancy, the deflagration flame rises in a
narrow cone towards the surface. For the most part, the main component of the flow of the
expanding ashes remains radial, but upon reaching the outer, low-pressure layers of the
white dwarf, an additional lateral component develops. This causes the deflagration ashes
to converge again at the opposite side, where the compression heats fuel and a detonation
may be launched. We first performed five three-dimensional hydrodynamic simulations of the
deflagration phase in 1.4
M⊙ carbon/oxygen white dwarfs at
intermediate-resolution (2563 computational zones). We confirm that the closer the
initial deflagration is ignited to the centre, the slower the buoyant rise and the longer
the deflagration ashes takes to break out and close in on the opposite pole to collide. To
test the GCD explosion model, we then performed a high-resolution (5123 computational zones)
simulation for a model with an ignition spot offset near the upper limit of what is still
justifiable, 200 km. This
high-resolution simulation met our deliberately optimistic detonation criteria, and we
initiated a detonation. The detonation burned through the white dwarf and led to its
complete disruption. For this model, we determined detailed nucleosynthetic yields by
post-processing 106
tracer particles with a 384 nuclide reaction network, and we present multi-band light
curves and time-dependent optical spectra. We find that our synthetic observables show a
prominent viewing-angle sensitivity in ultraviolet and blue wavelength bands, which
contradicts observed SNe Ia. The strong dependence on the viewing angle is caused by the
asymmetric distribution of the deflagration ashes in the outer ejecta layers. Finally, we
compared our model to SN 1991T. The overall flux level of the model is slightly too low,
and the model predicts pre-maximum light spectral features due to Ca, S, and Si that are
too strong. Furthermore, the model chemical abundance stratification qualitatively
disagrees with recent abundance tomography results in two key areas: our model lacks
low-velocity stable Fe and instead has copious amounts of high-velocity 56Ni and stable Fe. We therefore
do not find good agreement of the model with SN 1991T.
关键词：hydrodynamics;radiative transfer;methods: numerical;nuclear reactions, nucleosynthesis, abundances;supernovae: general;supernovae: individual: SN 1991T
