  Manual fits to spectral times series of Type Ia supernovae have provided a
method of reconstructing the explosion from a parametric model but due to lack
of information about model uncertainties or parameter degeneracies direct
comparison between theory and observation is difficult. In order to mitigate
this important problem we present a new way to probabilistically reconstruct
the outer ejecta of the normal Type Ia supernova SN 2002bo. A single epoch
spectrum, taken 10 days before maximum light, is fit by a 13-parameter model
describing the elemental composition of the ejecta and the explosion physics
(density, temperature, velocity, and explosion epoch). Model evaluation is
performed through the application of a novel rapid spectral synthesis technique
in which the radiative transfer code, TARDIS, is accelerated by a
machine-learning framework. Analysis of the posterior distribution reveals a
complex and degenerate parameter space and allows direct comparison to various
hydrodynamic models. Our analysis favors detonation over deflagration scenarios
and we find that our technique offers a novel way to compare simulation to
observation.
