2012ApJ...760...54M

We perform multi-dimensional, time-dependent radiation transfer simulations for hard X-ray and γ-ray emissions, following radioactive decays of ⁵⁶Ni and ⁵⁶Co, for two-dimensional delayed-detonation models of Type Ia supernovae (SNe Ia). The synthetic spectra and light curves are compared with the sensitivities of current and future observatories for an exposure time of 10⁶ s. The non-detection of the γ-ray signal from SN 2011fe at 6.4 Mpc by SPI on board INTEGRAL places an upper limit on the mass of ⁵⁶Ni of ≲ 1.0 M_☉, independently from observations in any other wavelengths. Signals from the newly formed radioactive species have not yet been convincingly measured from any SN Ia, but future X-ray and γ-ray missions are expected to deepen the observable horizon to provide high energy emission data for a significant SN Ia sample. We predict that the hard X-ray detectors on board NuStar (launched in 2012) or ASTRO-H (scheduled for launch in 2014) will reach to SNe Ia at ∼15 Mpc, i.e., one SN every few years. Furthermore, according to the present results, the soft γ-ray detector on board ASTRO-H will be able to detect the 158 keV line emission up to ∼25 Mpc, i.e., a few SNe Ia per year. Proposed next-generation γ-ray missions, e.g., GRIPS, could reach to SNe Ia at ∼20-35 Mpc by MeV observations. Those would provide new diagnostics and strong constraints on explosion models, detecting rather directly the main energy source of supernova light.