19 April 2010

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 multilevel,
multispecies 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 corecollapse 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, photoionization probabilities and forbidden transitions
in a true multilevel 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.
