I will present several projects to measure X-ray polarizations of astronomical sources over the next 5-10 yrs. Previous observations were obtained in 1970s for bright Galactic sources, e.g. X-ray binaries and the Crab Nebula, using a Bragg reflection from graphite crystals, limiting measurements to 2.6 and 5.2 keV. Recently, a few detections have been reported using Compton scattering at hard X-rays. A newly approved NASA mission is the Imaging X-ray Polarization Explorer (IXPE). It would operate in the 2-8 keV range and is expected to launch in late 2020. It has an imaging capability, with a resolution of about a half arc-minute, and should detect X-ray polarizations as low as 1-5 % for a dozen or more active galaxies, supernova remnants, neutron stars, and X-ray binaries during a mission lifetime of a few years. I will describe the instrument and a few of the science goals. I will also describe a design for a sounding rocket based polarimeter to work in the 0.2-0.6 keV band. The method uses gratings developed at MIT and multilayer coated mirrors. Potential targets include active galaxies, isolated neutron stars, and nearby black hole binaries in outburst. The configuration is extensible to orbital use, possibly to be combined with other instruments to provide a bandpass from 0.2 to 50 keV.
This talk will be followed by a tour of the X-ray polarimetry lab. Attendance of this talk is a prerequisite for taking the tour. Sign up for the tour at 2:20 immediately preceding the talk by Herman Marshall.