| Name: | SANGITA MAITI |
| Affiliation: | RISHI BANKIM CHANDRA COLLEGE |
| Conference ID : | ASI2024_1033 |
| Title : | A Comprehensive Study of Accretion Dynamics in XTE J1550-564 during 1998 and 2000 Outbursts |
| Authors : | SANGITA MAITI, BROJA GOPAL DUTTA, ANUJ NANDI |
| Authors Affiliation: | SANGITA MAITI, BROJA GOPAL DUTTA Affiliation Rishi Bankim Chandra College, Naihati-743165, India
ANUJ NANDI Affiliation U. R. Rao Satellite Centre, Bangalore-560037, India |
| Mode of Presentation: | Poster |
| Abstract Category : | High Energy Phenomena, Fundamental Physics and Astronomy |
| Abstract : | The spectro-temporal behavior provides us with a clear framework for understanding the accretion dynamics of an outbursting black hole source. The systematic evolution of time-lag and low-frequency quasi-periodic oscillations (LFQPOs) frequency implies a gradual drifting of the outer boundary of the Compton cloud during rising and declining outburst phases. We study the fast variability properties of Galactic Soft X-ray Transient (SXT) XTE J1550-564 during the 2000 outburst using RXTE instruments and compare the accretion scenario with the 1998 outburst. This variability study includes the study of Power Density Spectrum (PDS) and Fourier Frequency-dependent lag spectra with the variation of photon energy. We observe that QPO frequency gradually increases from ∼ 0.26 Hz to ∼ 4.53 Hz in 15 days and disappear. It starts to decrease smoothly in the declining phase and disappears after ∼ 13 days. We find a smooth variation in time-lag with QPO frequency, and the time-lag becomes negative, i.e., soft-lag at the QPO frequency > 3Hz. The time-lag again becomes hard-lag and increases gradually. In the previous 1998 outburst, the source took ∼ 12 days to reach QPO frequency from ∼ 81 mHz to ∼ 13.1 Hz, and in next 7 days it decreases to ∼ 2.62 Hz. A similar time-lag variation is also observed during the rising phase, where time-lag transition frequency was also > 3 Hz. We explain that this transitional frequency implies a specific size of the Comptonizing region, and subsequently, it gives rise to a characteristic length scale where the lag changes its sign. |
