Realistic inexpensive soft x-ray polarimeter and the potential scientific return

Abstract

Using multilayer coated mirrors to provide high reflectivity at large graze angles, we have proposed to launch a small telescope that is capable of measuring the linear polarization of the soft x-ray fluxes from many astronomical sources. Three identical mirror-detectoer assemblies are designed for maximum efficiency at 0.25 keV, where the photon spectra of many celestial targets peak. In observations lasting 1-3 days using this low risk instrument with proven heritage, we can detect polarizations of 5-10% at 5σ due to Compton scattering or synchrotron processes in the relativistic jets of BL Lac objects, accretion disks or jets in active galactic nuclei and atmospheres of isolated pulsars. Pulsar data can be binned by pulse phase to measure the orientation of the neutron star rotation and magnetic field axes and constrain the mass to radius ratio. This project has been selected for technology development funding by the NASA Explorer Program.