1. X-ray polarisation: Science
Accretion powered pulsars / high magnetic field neutron stars: X-ray beaming pattern (fan/pencil) is not known and will be determined from pulse phase resolved polarisation measurement. Rotation powered pulsars: The source of high energy emission is not known (polar cap / outer gap). Recent Fermi and Magic observations support outer gap model. Pulse phase resolved X-ray polarisation measurement of rotation powered pulsars is required. Black hole binaries: Multiple sources of X-ray polarisation – 1) reflection of coronal hard X-rays from the accretion disk, 2) thermal disk emission can be partially polarised in highly inclined sources, 3) in accretion disk around a highly spinning black hole, gravitational bending and reflection from the inner accretion disk can cause strong X-ray polarisation. SNR, Blazars, PWN can also have strong X-ray polarisation. Only one X-ray polarisation measurement of astronomical source, Crab (1976).

2. Accretion powered pulsars

3. Rotation powered pulsars & magnetars

4. X-ray polarisation in black hole accretion disk
Test of strong field gravity

5. X-ray polarisation measurement techniques
Bragg Reflection
Thompson Scattering
Photoelectron imaging

6. RRI Thomson X-ray Polarimeter
Polarisation is unexplored in High Energy Astrophysics
X-ray emission from the following processes should be polarised
Cyclotron
Synchrotron
Non-Thermal Bremsstrahlung
Scattering from non-spherical plasma
These objects should produce polarised X-ray radiation
Accretion powered pulsars
Rotation powered pulsars
Magnetars
Pulsar wind nebulae
Non-thermal supernova remnants
Black holes, micro-quasars and active galactic nuclei
Measurement Technique
Anisotropic Thomson Scattering
Crab nebula is the only source for
which X-ray polarisation measurement
exists. This was made in 1976 !!
The GEMS mission, to be launched
in 2014 will work in a different
energy band of 2-10 keV

7. Development status Results
A Thomson X-ray polarimeter has been designed, developed and successfully tested at RRI.
These have been made:
Detectors
Front end electronics
Processing electronics
Collimators with flat top response
Test and calibration setup
Rotational stage
Results
Light Curve
Power spectrum
Light Curve
Unpolarised source
Polarised source
Polarised source

8. X-ray polarimeter small satellite mission
Key features of the polarimeter
Minimum detectable Polarisation of 3%
at 5 sigma level for a 50 mCrab source
No of sources: 50
Weight: 110 kg
Data rate: 300 Mb per orbit
Spacecraft
Spinning satellite, 0.5 rpm
Very long exposures, one week to one month
Pointing accuracy: 0.1 degree
Equatorial orbit, less than 20 degree
Altitude: 500—600 km
Collimator
Scatterer
Detectors