Spectral evolution of magnetic flares and time lags in accreting black hole sources

摘要: We present a model for the short timescale spectral variability of accreting black holes. It describes well time-averaged spectra as temporal characteristics such power-density spectrum, time/phase lags, and coherence function Cygnus X-1. assume that X/gamma-rays are produced in compact magnetic flares at radii < 100GM/c^2 from central hole. The tendency loops to inflate detach underlying accretion disc causes spectrum flare evolve soft hard due decrease feedback cold disc, so causing time delays between photons. identify observed lags with evolution timescales flares, which order Keplerian timescale. overall using pulse avalanche each has certain probability trigger neighbouring flare, thus occasionally producing long avalanches. duration avalanches determines Fourier frequencies where most power emerges.