Abstract
The observations of the black hole binary Cygnus X-l were made in the energy band of 20–100keV with a balloon-borne Xenon-filled multiwire proportional counter telescope on 5th April 1992. Timing analysis of the data revealed the presence of Quasi-Periodic Oscillations (QPO) in the hard X-ray emission from the source. The QPO feature in the power density spectrum is broad with a peak at a frequency of 0.06 Hz. This result is compared with similar reports of QPOs in Cyg X-l in soft and hard X-rays. Short time scale random intensity variations in the X-ray light curve are described with a shot noise model.
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Paul, B., Agrawal, P.C. & Rao, A.R. Low frequency quasi-periodic oscillations in the hard x-ray emission from cygnus x-1. J Astrophys Astron 19, 55–61 (1998). https://doi.org/10.1007/BF02714891
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DOI: https://doi.org/10.1007/BF02714891