A model with a condensed iron surface and partially ionized hydrogen-thin atmosphere allows us to fit simultaneously the observed general spectral shape and the broad absorption feature ( observed at 0.3 keV ) in different spin phases of the isolated neutron star RBS 1223 .
We constrain some physical properties of the X-ray emitting areas , i.e .
the temperatures ( \mathrm { T } _ { pole 1 } \sim \mathrm { 105 eV,T } _ { pole 2 } \sim \mathrm { 99 eV } ) , magnetic field strengths ( \mathrm { B } _ { pole 1 } \approx \mathrm { B } _ { pole 2 } \sim \mathrm { 8.6 \times 10 ^ { 13 } G } ) at the poles , and their distribution parameters ( a1 \sim 0.61 , a2 \sim 0.29 , indicating an absence of strong toroidal magnetic field component ) .
In addition , we are able to place some constraints on the geometry of the emerging X-ray emission and the gravitational redshift ( \mathrm { z } \sim \mathrm { 0.16 ^ { 0.03 } _ { -0.01 } } ) of the isolated neutron star RBS 1223 .