Off-Axis Gamma-Ray Burst Afterglow Modeling Based On A Two-Dimensional
  Axisymmetric Hydrodynamics Simulation
  Starting as highly relativistic collimated jets, gamma-ray burst outflows
gradually decelerate and become non-relativistic spherical blast waves.
Although detailed analytical solutions describing the afterglow emission
received by an on-axis observer during both the early and late phases of the
outflow evolution exist, a calculation of the received flux during the
intermediate phase and for an off-axis observer requires either a more
simplified analytical model or direct numerical simulations of the outflow
dynamics. In this paper we present light curves for off-axis observers covering
the long-term evolution of the blast wave calculated from a high resolution
two-dimensional relativistic hydrodynamics simulation using a synchrotron
radiation model. We compare our results to earlier analytical work and
calculate the consequence of the observer angle with respect to the jet axis
both for the detection of orphan afterglows and for jet break fits to the
observational data. We find that observable jet breaks can be delayed for up to
several weeks for off-axis observers, potentially leading to overestimation of
the beaming corrected total energy. When using our off-axis light curves to
create synthetic Swift X-ray data, we find that jet breaks are likely to remain
hidden in the data. We also confirm earlier results in the literature finding
that only a very small number of local Type Ibc supernovae can harbor an orphan
afterglow.
