Nucleosynthesis and Gamma-Ray Line Spectroscopy with INTEGRAL
  Cosmic nucleosynthesis co-produces unstable isotopes, which emit characteristic gamma-ray emission lines upon their radioactive decay that can be measured with SPI on INTEGRAL. High spectral resolution allows to derive velocity constraints on nucleosynthesis ejecta down to ~100 km/s. Core-collapse supernovae apparently do not always produce significant amounts of 44Ti, as in the Galaxy fewer sources than expected from the supernova rate have been found. INTEGRAL's 44Ti data on the well-observed Cas A and SN1987A events are evidence that non-spherical explosions and 44Ti production may be correlated. Characteristic gamma-ray lines from radioactive decays of long-lived 26Al and 60Fe isotopes have been exploited to obtain information on the structure and dynamics of massive stars in their late evolution and supernovae, as their yields are sensitive to those details. The extended INTEGRAL mission establishes a database of sufficiently-deep observations of several specific regions of massive star groups, such as Cygnus, Carina, and Sco-Cen. In the inner Galaxy, 26Al nucleosynthesis gamma-rays help to unravel the Galaxy's structure and the role of a central bar, as the kinematically-shifted 26Al gamma-ray line energy records the longitude-velocity behavior of hot interstellar gas. Thus, INTEGRAL has consolidated the feasibility of constraining cosmic nucleosynthesis through gamma-ray line observations. Due to its extended mission INTEGRAL maintains its chance to also see rare sufficiently-nearby events, such as a nova to provide first nova nucleosynthesis measurements of 7Be and 22Na production. 
Roland Diehl
astro-ph.HE