AC1 - Spectral and Temporal properties of Black Holes and neutron stars and the theoretical models |
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Speaker |
Ghosh, Arindam |
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Coauthors |
Sandip K. Chakrabarti |
| Talk Title |
Evidence of Two Components in Accretion Flow from Timing Analysis with RXTE/ASM Data of several Black Hole Binaries |
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Abstract |
The results of timing analysis with RXTE/ASM (1.5-12 keV) X-ray data of several Galactic black hole binary sources (persistent, class-variable, and transient) are interpreted from the foundation of Two-Component Advective Flow (TCAF). This analysis shows the existence of two components in accretion flow in both low-mass and high-mass X-ray binaries (LMXBs & HMXBs). A large disk with long viscous timescale in the accretion with high angular momentum is omnipresent in LMXBs due to Roche lobe overflow, while a small disk with a little viscous delay is observed in HMXBs mainly for wind accretion. These two timescales of the two components give rise to a significant lag between their arrival times near a black hole. A large Keplerian disk in LMXBs must cause a larger time lag than that in HMXBs. To detect such a lag, we introduce an index ϴ, which acts like a proxy of the usual (i) hardness ratios, (ii) photon index, (iii) spectral index, and (iv) Comptonization efficiency at each instant of time. Classic method of direct cross-correlation between the two photon/energy fluxes seldom or never reveals the aforesaid lag. But when ϴ is considered as a reference variable, a significant time lag in LMXBs is observed. However, this lag is negligible in HMXBs. Temporal variation of ϴ also reveals spectral state transitions. In addition, more emphasis has been given to the outbursts in transient LMXBs, exhibiting either multiple (GX 339-4 and H 1743-322) or sporadic outbursts in order to show that the Keplerian disk varies in its size from an outburst to the other. This also dictates the fate of all outbursts. Furthermore, earlier results of spectral analysis with RXTE/PCA (2.5-25 keV) data are also used to confirm our findings. Moreover, both normal and failed (anomalous) outbursts can be distinguished from ϴ-behaviour alone. Outbursts, in general, are shown to fall into two types, based on four distinct features observed by us. |
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