  Numerical jet simulations serve a valuable role in calculating gamma-ray
burst afterglow emission beyond analytical approximations. Here we present the
results of high resolution 2D simulations of decelerating relativistic jets
performed using the RAM adaptive mesh refinement relativistic hydrodynamics
code. We have applied a separate synchrotron radiation code to the simulation
results in order to calculate light curves at frequencies varying from radio to
X-ray for observers at various angles from the jet axis. We provide a
confirmation from radio light curves from simulations rather than from a
simplified jet model for earlier results in the literature finding that only a
very small number of local Ibc supernovae can possibly harbor an orphan
afterglow.
  Also, recent studies have noted an unexpected lack of observed jet breaks in
the Swift sample. Using a jet simulation with physical parameters
representative for an average Swift sample burst, such as a jet half opening
angle of 0.1 rad and a source redshift of z = 2.23, we have created synthetic
light curves at 1.5 keV with artificial errors while accounting for Swift
instrument biases as well. A large set of these light curves have been
generated and analyzed using a Monte Carlo approach. Single and broken power
law fits are compared. We find that for increasing observer angle, the jet
break quickly becomes hard to detect. This holds true even when the observer
remains well within the jet opening angle. We find that the odds that a Swift
light curve from a randomly oriented 0.1 radians jet at z = 2.23 will exhibit a
jet break at the 3 sigma level are only 12 percent. The observer angle
therefore provides a natural explanation for the lack of perceived jet breaks
in the Swift sample.

High Energy Astrophysical Phenomena