Общемосковский семинар астрофизиков
имени Якова Борисовича Зельдовича

Повестка: 

1. Новости

проф.Липунов В.М., Часовников А.Р. (ГАИШ, ФФ МГУ)

 2. Timing and X-ray Spectral Analysis of  SSCyg. Constancy of the photon index in the X-ray spectrum

 проф.Титарчук Л.Г.(АКЦ ФИАН), Штуковский А., Арефьев В.(ИКИ)

 We studied the power and energy (photon) spectra of SS Cyg. We demonstrate that the power  density spectrum (PDS)  described by the white-red noise.  We also find the presence of a QPO in the range of    5x10^{-3} -5 x10^{-2} Hz  as a signature of the bounded medium surrounding a white dwarf (WD).  For the spectral analysis  weused the  RXTE and  NuStar data.  To explain the  X-ray  spectra  along with the PDS  we apply the transition layer (TL) model which  uses  an adjustment of the Keplerian disk to the slower rotation of the central WD. As a result the hot Compton corona (or TL)  is  naturally  formed near a a WD.  We also find that the best-fit   plasma (electron) temperature  of the TL is around 5 keV and it  is  significantly higher than the surrounding disk   temperature and that of the WD of order 0.1 keV and even less. The most important result of our study of the WD X-ray spectra is a relative constancy of the photon index, Gamma  within  an interval of 1.9+/- 0.1. This result is similar of that found for  neutron sources and drastically different for a black hole  for which was revealed an evolution of   Gamma following  the index saturation. It is worth  noting that  a value of the BH index saturation Gamma_{sat}  strongly depends of the plasma temperature of the converging flow and can change from 2 to 3..

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