Gamma-ray signatures of supernovae and hypernovae

We review the characteristics of nucleosynthesis and radioactivities in “hypernovae”, i.e., supernovae with very large explosion energies (≳1052 ergs) and their γ-ray line signatures. We also discuss the 44Ti line γ-rays from SN1987A and the detectability with INTEGRAL. Signatures of hypernova nucleosynthesis are seen in the large [(Ti, Zn)/Fe] ratios in very metal poor stars. Radioactivities in hypernovae compared to those of ordinary core-collapse supernovae show the following characteristics: 1) The complete Si burning region is more extended, so that the ejected mass of 56Ni can be much higher. 2) Si-burning takes place in higher entropy and more α-rich environment. Thus the 44Ti abundance relative to 56Ni is much larger. In aspherical explosions, 44Ti is even more abundant and ejected with velocities as high as ∼15,000 km s−1, which could be observed in γ-ray line profiles. 3) The abundance of 26Al is not so sensitive to the explosion energy, while the 60Fe abundance is enhanced by a factor of ∼3.