X-ray polarisation measurement is a unique tool which may provide crucial
information regarding the emission mechanism and the geometry of various
astrophysical sources, like neutron stars, accreting black holes, pulsar wind
nebulae, AGNs, Supernova Remnants etc. and can help us to probe matter under
extreme magnetic fields and extreme gravitational fields. Although the three
other domains of X-ray Astronomy i.e. timing, spectral and imaging are well
developed, there has been very little progress in X-ray Polarimetry with only
one definitive polarisation measurement and a few upper limits available so
far. Radiation from accreting black holes in their thermal dominated (High
Soft) state is expected to be polarised due to scattering in the plane parallel
atmosphere of the disk. Also, special and general relativistic effects in the
innermost parts of the disk predicts energy dependent rotation in the plane of
polarisation and some distinct signatures which can be used as a probe for
measuring the parameters of the black hole like its spin, emissivity profile
and the angle of inclination of the system. We present the results from an
analysis of expected minimum detectable polarisation from some of the galactic
black hole binaries GRO J1655-40, GX339-4, H1743-322, Cyg X-1 and XTE J1817-330
in their thermal dominated state with a proposed Thomson X-ray Polarimeter. A
proposal for a scattering polarimeter has been submitted to the Indian Space
Research Organization (ISRO) for a dedicated small satellite mission and a
laboratory unit has been built. Along with the measurement of the degree of
polarisation, the polarisation angle measurement is also important, hence the
error in the polarisation angle measurement for a range of detection
significance is also obtained.Comment: 12 pages, 13 figures, 2 tables, accepted for publication by MNRA
