Model Spectra for GX 17+2 in the Flaring and Horizontal Branches

GX 17+2, a bright low-mass X-ray binary, was observed with the X-ray satellite Ginga in 1989. Remarkable correlation curves of this source in both the X-ray color-color and color-intensity diagrams determine the physical parameters in model spectra comprising a hard blackbody component and a multicolor disk component. Fittings of the model spectra with observations in the color-color and color-intensity diagrams reveal that the effective temperatures and the innermost radius of the accretion disk remain stable, whereas the emission area and the effective temperature of the hard blackbody component, presumably emitted from the neutron-star surface, are variable.