New Insights from Cosmic Gamma-Ray Line Observations
Tuesday 27 October 2015
to 15:00 at
Roland Diehl (MPE, Garching)
Gamma-ray lines from cosmic sources arise from radioactive decay of unstable isotopes co-produced by nucleosynthesis, from energetic collisions among atomic nuclei which may excite nuclei above their ground level, and from interstellar annihilation of positrons ejected from a variety of candidate sources. Such gamma-ray lines are being measured with ESA’s INTEGRAL space mission since its launch in 2002, and complement the earlier survey of NASA’s Compton Gamma-Ray Observatory with precision spectroscopy. The nuclei seen by those missions in their characteristic gamma-rays are mainly 56Ni, 57Ni, 44Ti, 26Al, and 60Fe, each from their characteristic sources; also positron annihilation has been measured and mapped throughout the Galaxy both in the 511 keV line and positronium continuum. The current NuSTAR mission now adds observations at the low-energy end for 44Ti decay with an imaging X-ray telescope. In this talk we present those observations and discuss their implications.