ИСТИНА

We present an analysis of the X-ray spectral properties observed from the atoll-source 4U1705-44 during evolutions between island and banana states. We analyze observations using the RXTE and BeppoSAX. We find that the X-ray broad-band energy spectra during all spectral states can be adequately reproduced by a model, consisting a low-temperature Blackbody component, two Comptonized components arising from the seed photons coming from a neutron star (NS) atmosphere at a temperature kT_{s1}~1.5 keV (herein Comptb1) and a second resulting from the seed photons of T_{s2}=1.1-1.3 keV coming from the disk (herein Comptb2). We also include an iron-line (Gaussian) component in the spectra. The data analysis using this model indicates that the photon power-law index Gamma_1 of our model is almost constant (Gamma_1~2) for all spectral states. Another parameter, Gamma_2 demonstrates a two-phase behavior depending on the spectral state. Gamma_2 is quasi-constant at Gamma_2~2 when the electron temperature kT^{(2)}_e<80 keV and Gamma_2 is less than 2, namely in the range of 1.3<Gamma_2<2, when kT^{(2)}_e>80 keV. We also detect a decrease of kT_{s2} from 1.3 keV to 1.1 keV during this high electron temperature phase. This phase is similar to that was previously found in the Z-source Sco X-1. We interpret the decreasing index phase using a model in which a high radiation pressure from the NS causes an expansion of the Compton cloud similar to that found previously in ScoX-1 during the Flaring branch.