A fully 3D Monte Carlo scheme is applied to compute optical bolometric light
curves for aspherical (jet-like) supernova explosion models. Density and
abundance distributions are taken from hydrodynamic explosion models, with the
energy varied as a parameter to explore the dependence. Our models show
initially a very large degree (∼4 depending on model parameters) of
boosting luminosity toward the polar (z) direction relative to the equatorial
(r) plane, which decreases as the time of peak is approached. After the peak,
the factor of the luminosity boost remains almost constant (∼1.2) until
the supernova enters the nebular phase. This behavior is due mostly to the
aspherical 56Ni distribution in the earlier phase and to the disk-like
inner low-velocity structure in the later phase. Also the aspherical models
yield an earlier peak date than the spherical models, especially if viewed from
near the z-axis. Aspherical models with ejecta mass \sim 10\Msun are
examined, and one with the kinetic energy of the expansion ∼2±0.5×1052 ergs and a mass of 56Ni \sim 0.4\Msun yields a light
curve in agreement with the observed light curve of SN 1998bw (the prototypical
hyper-energetic supernova). The aspherical model is also at least qualitatively
consistent with evolution of photospheric velocities, showing large velocities
near the z-axis, and with a late-phase nebular spectrum. The viewing angle is
close to the z-axis, strengthening the case for the association of SN 1998bw
with the gamma ray burst GRB980425.Comment: Accepted by the Astrophysical Journal. 28 pages, 14 figure