The observed high energy power-law tail of high soft ( HS ) state , and steep power law ( SPL ) state of X-ray binaries can be generated by the bulk Comptonization process with a free-fall bulk region onto the compact object .
We study these high energy tails by considering a bulk region arisen due to a right circular conical outflow ( of opening angle \theta _ { b } with axis perpendicular to the disk ) from the disk , using a Monte Carlo scheme .
Out of two possible bulk directions , i ) along the surface of the cone , ii ) inside the conic region , we find that a ) the randomness of bulk directions is increased with increasing \theta _ { b } , b ) the emergent spectrum has a power-law component in the observed range of photon index \Gamma ( > 2.4 ) in both cases for \theta _ { b } greater than \sim 30 degree , even for a low medium temperature .
For given \Gamma , the optical depth for lower opening angle has comparatively high value than the case with larger opening angle of conical outflow .
Similarly the bulk speed is higher for smaller opening angle .
It seems that the lower opening angle outflow can provide the observed high energy tail in both the states HS and SPL .
We notice that when the outflow is collimated or conical flow ( \theta _ { b } < 30 ) then the emergent spectrum does not have power-law component unless it is observed in thermal Comptonized spectrum .