Science with IXPE
TECHNICAL AND SCIENCE OBJECTIVES
The primary technical and science objectives of IXPE are:
- Improving polarization sensitivity by two orders of magnitude over the X-ray polarimeter aboard the Orbiting Solar Observatory OSO-8.
- Providing simultaneous spectral, spatial, and temporal measurements.
- Determining the geometry and the emission mechanism of Active Galactic Nuclei and microquasars.
- Finding the magnetic field configuration in magnetars and determining the magnitude of the field.
- Finding the mechanism for X ray production in pulsars (both isolated and accreting) and the geometry.
- Determining how particles are accelerated in Pulsar Wind Nebulae.
IXPE uses X-ray polarimetry to dramatically expand X-ray observation space, which historically has been limited to imaging, spectroscopy, and timing. This advance will provide new insight as to how X-ray emission is produced in astrophysical objects, especially systems under extreme physical conditions—such as neutron stars and black holes. Polarization uniquely probes physical anisotropies—ordered magnetic fields, aspheric matter distributions, or general relativistic coupling to black-hole spin—that are not otherwise easily measurable.
IXPE complements all other investigations in high-energy astrophysics by adding the important and relatively unexplored dimensions of polarization to the parameter space for exploring cosmic X-ray sources and processes, and for using extreme astrophysical environments as laboratories for fundamental physics.
The scientific drivers
IXPE scientific requirements descend from the expected polarization properties of the celestial sources and their temporal, spectral and angular characteristics. The sensitivity of IXPE, as shown in the same table, is set for meaningful polarimetry, with realistic observing time, of the brightest AGNs.
The following table flows down the scientific requirements into instrument requirements.
|Modulation factor||> 27.7 at 2.6 keV (with 20 % cut)|
|Modulation factor||> 53.7 at 6.4 keV (with 20 % cut)|
|Spurious modulation||< 0.27 % at 5.9 keV|
|GPD quantum efficiency||> 17.7 % at 2.6 keV|
|GPD quantum efficiency||> 1.8 % at 6.4 keV|
|Energy resolution||1.5 keV (at 5.9 keV)|
|Knowledge of the spurious modulation||< 0.1 % at ... keV|
|Systematic error on angle||< 0.4 deg|
|Position resolution (HEW)||< 190 μm at 2.3 keV|
|Dead time||< 1.2 ms (average at 3 keV)|
|Maximum counting rate||900 c/s|
|Time accuracy||± 94 μs (99 %)|
|Background||< 0.004 s-1 cm-2 per DU (2-8 keV)|
Updated on September 12, 2021