Integral observations of polarization: From the Crab pulsar to Cygnus X-1

In complement to spectro-imaging observations, γ-ray polarimetry provides a unique insight into the geometry and magnetic configuration of compact γ-ray sources, such as neutron stars or black holes. Due to the unprecedented spectral and timing capabilities of Integral, and thanks to its coded mask imaging technics, which efficiently suppresses most of the background contribution, we have measured linearly polarized emission from the brightest cosmic high energy sources with the two telescopes IBIS and SPI. We were able to measure for the first time, at energies above 200 keV, a clear polarization signal from different types of γ-ray sources such as the Crab pulsar and nebula, the black hole candidate Cygnus X-1, and Gamma-Ray Bursts. These observations have enabled us to put strong constraints on the physical process at work in these sources, and the achieved sensitivity opens a new window for polarimetric studies in the soft γ-ray regime.