XEUS is a large area telescope aiming to rise X-ray Astronomy to the level of Optical Astronomy in terms of collecting areas. It will be based on two satellites, locked on a formation flight, one ...with the optics, one with the focal plane. The present design of the focal plane foresees, as an auxiliary instrument, the inclusion of a Polarimeter based on a Micropattern Chamber. We show how such a device is capable to solve open problems on many classes of High Energy Astrophysics objects and to use X-ray sources as a laboratory for a substantial progress on Fundamental Physics.
X-Ray Polarimetry can be now performed by using a Micro Pattern Gas Chamber in the focus of a telescope. It requires large area optics for most important scientific targets. But since the technique ...is additive a dedicated mission with a cluster of small telescopes can perform many important measurements and bridge the 40 year gap between OSO-8 data and future big telescopes such as XEUS. POLARIX has been conceived as such a pathfinder. It is a Small Satellite based on the optics of JET-X. Two telescopes are available in flight configuration and three more can be easily produced starting from the available superpolished mandrels. We show the capabilities of such a cluster of telescopes each equipped with a focal plane photoelectric polarimeter and discuss a few alternative solutions.
Development of multi-layer optics makes feasible the use of X-ray telescope at energy up to 60-80 keV: in this paper we discuss the extension of photoelectric polarimeter based on Micro Pattern Gas ...Chamber to high energy X-rays. We calculated the sensitivity with Neon and Argon based mixtures at high pressure with thick absorption gap: placing the MPGC at focus of a next generation multi-layer optics, galatic and extragalactic X-ray polarimetry can be done up till 30 keV.
The polarisation of x-ray photons can be determined by measuring the direction of emission of a K-shell photoelectron. Effective exploitation of this effect below 10 keV would allow development of a ...highly sensitive x-ray polarimeter dedicated in particular to x-ray astronomy observations. Only with the advent of finely segmented gas detectors was it possible to detect polarisation sensitivity based on the photoelectric effect in this energy range. Simulation and measurements at 5.4 and 8.04 keV with a microgap gas counter, using both a polarised and an unpolarised x-ray source, showed that the photoelectron track in a neon-based gas mixture retains the memory of the polarisation of the incoming photons. Possible experiments aimed at galactic/extragalactic sources and solar flares are considered and their sensitivity to these sources is calculated.
Using observations of X-ray pulsar Her X-1 by the Imaging X-ray Polarimetry Explorer, we report on a highly significant (\(>17\sigma\)) detection of the polarization signal from an accreting neutron ...star. The observed degree of the linear polarization of \(\sim\)10\% is found to be far below theoretical expectations for this object, and stays low throughout the spin cycle of the pulsar. Both the polarization degree and the angle exhibit variability with pulse phase, which allowed us to measure the pulsar spin position angle 57(2) deg and the magnetic obliquity 12(4) deg, which is an essential step towards detailed modelling of the intrinsic emission of X-ray pulsars. Combining our results with the optical polarimetric data, we find that the spin axis of the neutron star and the angular momentum of the binary orbit are misaligned by at least \(\sim\)20 deg, which is a strong argument in support of the models explaining stability of the observed super-orbital variability with the precession of the neutron star.
