  In gauge theory of gravity, there is direct coupling between the spin of a
particle and gravitomagnetic field. In the surface of a neutron star or near
black hole, the coupling energy between spin and gravitomagnetic field can be
large and detectable. Precise measurement of the position of spectrum lines of
the corresponding emission or absorption can help us to determine the
gravitomagnetic field and electromagnetic field simultaneously. The ratio
$\frac{\Delta E_e}{\Delta E_p}$ can be served as a quantitative criteria of
black hole. In GRBs or X-ray pulsar, absorption spectral lines of electron were
observed. If the absorption spectral lines of electron and proton can be
observed simultaneously, using the method given in this paper, we can determine
the gravitomagnetic field in the surface of the star, and discriminate black
hole from neutron star.
