Hard X- and \gamma -ray spectra and light curves resulting from radioactive decays are computed for aspherical ( jet-like ) and energetic supernova models ( representing a prototypical hypernova SN 1998bw ) , using a 3D energy- and time-dependent Monte Carlo scheme .
The emission is characterized by ( 1 ) early emergence of high energy emission , ( 2 ) large line-to-continuum ratio , and ( 3 ) large cut-off energy by photoelectric absorptions in hard X-ray energies .
These three properties are not sensitively dependent on the observer ’ s direction .
On the other hand , fluxes and line profiles depend sensitively on the observer ’ s direction , showing larger luminosity and larger degree of blueshift for an observer closer to the polar ( z ) direction .
Strategies to derive the degree of asphericity and the observer ’ s direction from ( future ) observations are suggested on the basis of these features , and an estimate on detectability of the high energy emission by the INTEGRAL and future observatories is presented .
Also presented is examination on applicability of a gray effective \gamma -ray opacity for computing the energy deposition rate in the aspherical SN ejecta .
The 3D detailed computations show that the effective \gamma -ray opacity \kappa _ { \gamma } \sim 0.025 - 0.027 cm ^ { 2 } g ^ { -1 } reproduces the detailed energy-dependent transport for both spherical and aspherical ( jet-like ) geometry .