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X-ray polarisation: Science

X-ray polarisation: Science.

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X-ray polarisation: Science

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  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 Measurement Technique Anisotropic Thomson Scattering 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 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 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 Polarised source Unpolarised source Polarised source

  8. X-ray polarimeter small satellite mission Collimator Scatterer Detectors 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

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