NORMALIZED POWER SPECTRAL DENSITIES OF 2 X-RAY COMPONENTS FROM GS-1124-683

Time variations of X-rays from the black hole candidate GS 1124-683 are investigated. In the high stare, X-rays consist of two energy spectral components, i.e., a power-law component and a disk blackbody component. Power spectral densities (PSDs) of these two energy spectral components have characteristic shapes. The PSD of the power-law energy spectral component has a flat top (FT noise function) at frequencies less than about 2 Hz, and the PSD of the disk blackbody component has a power-law shape (PL noise function). The FT noise functions normalized by the power-law energy spectral component (the normalized FT noise function) are almost the same in cases where the photon counts in the power-law energy spectral component are larger than about 20% of the total photon counts; however, there are a few exceptions. The PL noise functions normalized by the disk blackbody component (the normalized PL noise function) are also almost the same when the photon counts in the power-law component are less than about 10%. However, the normalized PL noise functions have a tendency to increase with the power-law component, when the photon counts in the power-law component are larger than about 10%. This shows that time variations of the disk blackbody component have some relation to those of the power-law energy spectral component. In the high-to-low transition state, the normalized PSD (NPSD) of the power-law energy spectral component (the normalized FT noise function) is 4 times larger than the value in the high state, although the energy spectrum of this component is the same as that in the high state. In the low state, the X-rays consist of mainly a power-law energy spectral component and this component has a harder spectrum than the power-law energy spectral component in the high state. Moreover, the NPSD of X-rays in the low state has also a flat top at frequencies less than about 0.1 Hz and has larger absolute values than those of the normalized FT noise function of the power-law energy spectral component in the high state. As the phase legs between time variations of different energy X-rays are also different in these two states, the power-law energy spectral components in the high and the low state should have different production processes. Models that produce these energy spectral components are discussed.