Abstract

The complex behavior of Fourier phase lags associated to Quasi-Periodic Oscillations (QPOs) is one of the most significant observational effects of Galactic black hole sources. This temporal property can diagnoses the dynamics of accretion flow around the black holes. We analyze RXTE/PCA data of the black hole source XTE J1550-564 for the 1998 outburst. We find smooth decrease of the time lag(s) with time in the rising phase and in the declining phase, its increases with time. We conclude that this variation could be due to the movement of the comptonizing region itself. We also find that evolution of phase/time lag is correlated with the QPO frequency. This behavior suggests towards a common evolution scenario of the black hole transient XTE J1550-564 through its outburst.