38 - Programs of X-ray polarimetry in Italy

Summary

Programs of X-ray polarimetry in Italy arise from the convergence of a long experience of X-ray astronomy missions with an outstanding tradition in development of radiation detectors. The gas pixel detector in the focus of X-ray optics can perform angular-resolved polarimetry with a breakthrough improvement in sensitivity, even with a moderate collecting surface. POLARIX makes a large use of already existing items and, in particular, of the three telescopes from the JET-X program. It can extend the X-ray polarimetry from one positive detection only, to tens of sources, including a few brighter extragalactics: an ambitious pathfinder on a very limited budget. Phase A study of POLARIX, and of four other missions, was performed in 2008 and ASI should select two missions to fly. Another pathfinder is under study: two short telescopes, designed with modern tight packing techniques, mounted as piggy-back on the Chinese mission HXMT.

The national context

X-ray polarimetry has been a line of research at IASF for many years. A scattering polarimeter was proposed for the XMM mission, but was not selected. An IASF team joined the collaboration headed by R. Novick for the Stellar X-ray Polarimeter, aboard the Spectrum X-Gamma mission, contributing the detectors as the sensors for both scattering and diffraction stages. SXRP was completed but the whole mission was not. Considering the large area of the telescope, SXRP was close to the best achievable with conventional techniques.