144 research outputs found
Type Ia supernovae: differences due to progenitors within delayed detonation explosions
At this moment, the use of SNIa for cosmology lies on the assumption that the
SNe at high redshifts are equal to the local ones. However, some observations
indicate a correlation between the light curve (LC) properties and the
morphological type of the host galaxy. This could indicate a dependence with
the age (mass/composition) of the underlying population. In this work we have
chosen the delayed detonation explosion model in CO Chandrasekhar mass WDs to
explore the dependence of the SNIa LC and nucleosynthesis with the initial mass
and composition of the WD progenitor. The progenitor influences the final SNIa
via the mass of the CO core formed and the C/O ratio within it (1D explosion
models). We have followed the evolution of stars with masses between 1.5 and 8
Mo and metallicity, Z=0, 1.E-05, 0.001 and 0.02, from the pre-main sequence to
the TP-AGB phase. The differences obtained in the final C/O ratio within the
explosive WD are smaller than 22%. This results in a difference at maximum of
0.03 mag and of 0.1 mag when the brightness-decline relation is applied.Comment: 4 pages, 1 figure, needs espcrc1.sty; conference "Nuclei in the
Cosmos 2000", held in Arhus, Denmark, June 27-July 1, 2000; submitted to
Nucl. Phys.
The 2D Distribution of Iron Rich Ejecta in the Remnant of SN 1885 in M31
We present Hubble Space Telescope (HST) ultraviolet Fe I and Fe II images of
the remnant of Supernova 1885 (S And) which is observed in absorption against
the bulge of the Andromeda galaxy, M31. We compare these Fe I and Fe II
absorption line images to previous HST absorption images of S And, of which the
highest quality and theoretically cleanest is Ca II H & K. Because the remnant
is still in free expansion, these images provide a 2D look at the distribution
of iron synthesized in this probable Type Ia explosion, thus providing insights
and constraints for theoretical SN Ia models. The Fe I images show extended
absorption offset to the east from the remnant's center as defined by Ca II
images and is likely an ionization effect due to self-shielding. More
significant is the remnant's apparent Fe II distribution which consists of four
streams or plumes of Fe-rich material seen in absorption that extend from
remnant center out to about 10,000 km/s. This is in contrast to the remnant's
Ca II absorption, which is concentrated in a clumpy, roughly spherical shell at
1000 to 5000 km/s but which extends out to 12,500 km/s. The observed
distributions of Ca and Fe rich ejecta in the SN 1885 remnant are consistent
with delayed detonation white dwarf models. The largely spherical symmetry of
the Ca-rich layer argues against a highly anisotropic explosion as might result
from a violent merger of two white dwarfs.Comment: 14 pages, 8 figures, and 1 table; revised to match ApJ published
versio
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