Temporal and Spectral Correlations of Cygnus X‐1

Abstract

Temporal and spectral properties of X-ray rapid variability of Cyg X-1 are studied through correlation analysis in the time domain on di †erent timescales. The correlation coefficients between the total intensity in the 2È60 keV band and the hardness ratio of the 13È60 keV to the 2È6 keV band on the timescale of D1 ms are always negative in all states. For soft states, the correlation coefficients are positive on all timescales from D0.01 to D100 s, which is signiÐcantly di †erent from those for transition and low states. The temporal structures in the high-energy band are narrower than those in low-energy band in quite a few cases. The delay of high-energy photons relative to low-energy ones in the X-ray variations has also been revealed by the correlation analysis. The implications of the observed temporal and spectral characteristics for the production region and mechanism of Cyg X-1 X-ray variations are discussed.

Phenomenological Analogies in TeV Blazars and Black Hole X-ray Binaries in Low State

“…This dependence is quite similar to those of BHXRBs such as Cyg X-1 in the low/hard states obtained with RXTE (e.g., Li, Feng & Chen 1999;Nowak et al 1999). Both showed a power law trend of hard lags as a function of Fourier frequency with the form τ lag ∼ ν −1 , where τ lag is the hard lag, and ν is Fourier frequency.…”

Strong correlation between the peak power density in the time domain and the luminosity of long γ-ray bursts

“…As actual GRBs usually have rather short durations, the light curve is not divided into segments when calculating the time-domain power density spectrum with the method given in Section 2.1, i.e., the number of segments M is taken to be 1 in the formalism of Li Ti-pei et al [7] . Moreover, since for the light curves of GRBs, the power density corresponding to tinle scale At should reflect all the properties of the light curve on this time scale, so we have to consider the fact that the way of combining channels to a given time scale At is not unique, i.e., we have to consider the effect of channel combination on the phase.…”

“…By taking tile light curve of Fig.la as one element, a light curve with a duration of 960see is duplicated, and the segmented processing is performed according to the timedomain method suggested by Li Ti-pei et al [7]. The calculated time-domain power density spectrum is in agreement with the non-segmented spectrum (Fig.lb), and this indicates that the method of variability analysis in the time domain is suitable for studying the real light curves of GRBs with limited durations.…”

Two‐dimensional Monte Carlo/Fokker‐Planck Simulations of Flares in Accretion Disk Corona Models

“…However, in a few cases, such as the Galactic microquasar GRS 1915+105 and XTE J1550À564, soft lags are occasionally observed, which sometimes alternate in sign between subsequent harmonics of a variable-frequency quasi-periodic oscillation (QPO; Cui 1999b; Reig et al 2000;Lin et al 2000b;Wijnands, Homan, & van der Klis 1999;Cui, Zhang, & Chen 2000). However, light-curve analysis in the time domain generally shows that such time lags are not associated with any significant misalignment of the peaks of individual microflares or shots in the light curves at different photon energies (Paul et al 1998a(Paul et al , 1998bMaccarone, Coppi, & Poutanen 2000) but rather are due to light-curve asymmetries and spectral evolution (e.g., Li, Feng, & Chen 1999).…”