Off-center observers versus supernovae in inhomogeneous pressure
  universes
  Exact luminosity distance and apparent magnitude formulas are applied to
Union2 557 supernovae sample in order to constrain possible position of an
observer outside of the center of symmetry in spherically symmetric
inhomogeneous pressure Stephani universes which are complementary to
inhomogeneous density Lema\^itre-Tolman-Bondi (LTB) void models. Two specific
models are investigated. The first which allows a barotropic equation of state
at the center of symmetry with no scale factor function being specified (model
IIA), and the second which has no barotropic equation of state at the center,
but has an explicit dust-like scale factor evolution (model IIB).
  It is shown that even at $3\sigma$ CL, an off-center observer cannot be
further than about 4.4 Gpc away from the center of symmetry which is comparable
to the reported size of a void in LTB models with the most likely value of the
distance from the center about 341 Mpc for model IIA and 68 Mpc for model IIB.
The off-center observer cannot be farther away from the center than about 577
Mpc for model IIB at $3\sigma$ CL. It is evaluated that the best-fit parameters
which characterize inhomogeneity are: $\Omega_{inh} = 0.77$ (dimensionless -
model IIA) and $\alpha = 7.31 \cdot 10^{-9}$ $(s/km)^{2/3} Mpc^{-4/3}$ (model
IIB).
