Аннотация:We present spectral signatures of neutron stars (NSs) and white dwarfs (WDs) hosted in accreting X-ray binaries that can be easily identified in X-ray observations. We perform spectral and timing analysis of 4U 1636–53 and SS Cygni, as typical representatives of such NS and WD binaries, based on their X-ray observations by RXTE, ASCA, Suzaku and BeppoSAX uising Comptonization spectral model. As a result, we formulate a criterion that makes it easy to distinguish NS from WD in such binaries: NS X-rays exhibits quasi-stable behavior with the index Γ → 2 and is characterized by quasi periodic oscillations (QPOs) at νQPO > 0.5 Hz, although WD X-rays is stable with Γ → 1.85 and is accompaniedby QPOs at νQPO < 0.05 Hz during source outbursts. In addition, we revealed that in 4U 1636–53 the mHz QPOs anti-correlate with the plasma temperature,Te of Compton cloud (or the corona around a NS. This allowed us to associate mHz-QPOs with the corona dynamics during outburst cycle. The above index effect, now well established for 4U 1636–53 and SS Cygni using extensive observations,has previously been found in other low-mass X-ray NS and WD binaries and agrees well with the criterion for distinguishing NSs and WDs presented here.
