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19 April 2010
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Soma De (U Oklahoma)
'Time dependent radiative transfer in SNe atmosphere and cosmic recombination epoch: Effect on spectra and transition probabilities in a true multilevel framework'
The radiative transfer equation (RTE) is effectively the Boltzman
equation for photons. This requires one to account for all possible
transition rates connecting all energy levels in a given system of
species (involving atoms, ions, or molecules). These rates depend
on the local radiation intensity and vice versa. This makes the
nature of the equations involved in such a scenario highly coupled
and the size of the problem very large, especially in a multi-level,
multi-species system. I will describe the scope of our general purpose
stellar atmosphere code PHOENIX to handle such problems focusing on
the cases of SNe and cosmic recombination. I will emphasize my
results on core-collapse supernova 1999em and SN1987A atmospheres
describing how time dependence in the rate equation arising from
long recombination time of hydrogen could affect the Balmer line
profile in a supernova's lifetime. I will also describe the effect
of escape, photo-ionization probabilities and forbidden transitions
in a true multi-level calculation where no assumptions of equilibrium
between the higher bound states were made. PHOENIX can also be
applied during cosmic recombination epoch. I will present preliminary
results on the electron fraction during the the recombination epoch
which is obtained by following a time dependent RTE through cosmic
recombination. These calculations should shed light on the understanding
of CMB power and polarization spectra.
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