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On variations of the brightness of type Ia supernovae with the age of the host stellar population
Recent observational studies of type Ia supernovae (SNeIa) suggest
correlations between the peak brightness of an event and the age of the
progenitor stellar population. This trend likely follows from properties of the
progenitor white dwarf (WD), such as central density, that follow from
properties of the host stellar population. We present a statistically
well-controlled, systematic study utilizing a suite of multi-dimensional SNeIa
simulations investigating the influence of central density of the progenitor WD
on the production of Fe-group material, particularly radioactive Ni-56, which
powers the light curve. We find that on average, as the progenitor's central
density increases, production of Fe-group material does not change but
production of Ni-56 decreases. We attribute this result to a higher rate of
neutronization at higher density. The central density of the progenitor is
determined by the mass of the WD and the cooling time prior to the onset of
mass transfer from the companion, as well as the subsequent accretion heating
and neutrino losses. The dependence of this density on cooling time, combined
with the result of our central density study, offers an explanation for the
observed age-luminosity correlation: a longer cooling time raises the central
density at ignition thereby producing less Ni-56 and thus a dimmer event. While
our ensemble of results demonstrates a significant trend, we find considerable
variation between realizations, indicating the necessity for averaging over an
ensemble of simulations to demonstrate a statistically significant result.Comment: 5 pages, 4 figures, 1 table, accepted to ApJ
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