  Electromagnetic observations of the first binary Neutron Star (BNS) merger
GW170817 has established that relativistic jets can be successfully launched in
BNS mergers. Typically, such jets produce emission in two phases: $\gamma$-ray
prompt emission and multi-wavelength afterglow. Due to relativistic
de-boosting, the detectability of both these counterparts is dependent on the
angle ($\theta_v$) between the observer's line of sight and the jet axis. We
compare the detectability of prompt and afterglow emission from off-axis jets,
assuming standard detector thresholds. We find that for top-hat jets, afterglow
is a more potential counterpart than the prompt emission even with unfavorable
afterglow parameters. For structured jets with a Gaussian profile, prompt
emission is more promising than the afterglows at extreme viewing angles, under
the assumption that the energy emitted in the prompt phase equals the kinetic
energy of the outflow. Assuming a Gaussian jet profile, we forecast the
population of $\gamma$-ray detections and find that extreme viewing angle
events like GRB170817A will be rare. In our simulated sample, the observed
isotropic equivalent energy in $\gamma$-rays is moderately correlated with the
viewing angle, such that a low $E_{\rm iso, \gamma}$ is almost always
associated with a high off-axis viewing angle.

High Energy Astrophysical Phenomena