POLAR

56 years after their discovery (1960 Vela satellites), gamma ray bursts (GRBs) are still full of mysteries. The production mechanism of these very intense explosions in the universe is still unknown. To validate or exclude existing models about their creation, a precise measurement of the polarization of the GRB is an important input. But, measuring convincingly the polarization of GRBs is a difficult experimental challenge, because GRBs are rare events that happen at random locations and times in the universe. Thus, existing general purpose detectors cannot properly measure the polarization and existing results are often unprecise and controversial.

The POLAR detector design is a dedicated polarimeter:

• The Compton Scattering Effect is used to measure the polarization of incoming photons.
• POLAR makes no attempt to do a precise localization of the GRB in the sky. This greatly simplifies the design of the detector. Currently, special purpose satellites like SWIFT can provide this information immediately. Many future satellites will have similar capabilities. To complement this, POLAR can roughly localize strong GRBs independently and with sufficient precision for a stand-alone measurement (preprint)
• Further publications of the POLAR collaboration.