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Astron. Astrophys. 330, 181-188 (1998)

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5. Conclusions

We have analyzed the data obtained from the Indian X-ray Astronomy Experiment (IXAE) on Cyg X-1 in its two spectral states. A method is evolved for background subtraction. The timing analysis has shown that:

1. The power density spectrum (PDS) shows substantial differences in the two spectral states: the power-law index between 0.03 to 0.3 Hz changed from -0.09 to -1.02 when the source changed from the hard to the soft state.

2. A new component in the PDS below 0.03 Hz has been identified and this component appears to be independent of the spectral state.

3. The shot statistics like the duration and the energy in shots show exponential distribution and the time constant shows significant difference in the two spectral states.

4. A large individual shot has been identified and it has an exponential rise and decay with a time constant of 0.4 s.

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© European Southern Observatory (ESO) 1998

Online publication: January 8, 1998