1997/10/24 by A. R. Rao, Rao, A. R., P. C. Agrawal +3
Engineering · Mathematics · Physics and Astronomy · #Accretion (finance) #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics (astro-ph) #Black hole (networking) #Detector #Exponential decay #Exponential function #FOS: Physical sciences #Laser-Plasma Interactions and Diagnostics #Light curve #Mathematics #Mechanics and Biomechanics Studies #Nuclear physics #On board #Optics #Physics #Proportional counter #Shot (pellet) #Spectral density #Spectral line #Statistics #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9710284
17 pages including 8 figures. To appear in Astronomy and Astrophysics
arxiv created 1997/10/24 · openalex publication_date 1997/10/24 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We present the time variability characteristics of Cygnus X-1 in its two\nspectral states. The observations were carried out using the Pointed\nProportional Counters (PPC) on-board the Indian X-ray Astronomy Experiment\n(IXAE). The details of the instrument characteristics, the observation\nstrategy, and the background modeling methods are described. In the soft state\nof Cyg X-1, we confirm the general trend of the Power Density Spectrum (PDS)\nobtained using the Proportional Counter Array (PCA) on-board the RXTE\nsatellite. The hard state of the source just prior to the spectral transition\nwas not observed by the PCA and we present the PDS obtained in this state. We\nfind that the low frequency end of the PDS is flatter than that observed during\nthe spectral transition. Additionally, we find that there is one more component\nin the low frequency end of the PDS, which is independent of the spectral state\nof the source. The time variability is also examined by taking the statistics\nof the occurrence of shots and it is found that the shot duration and shot\nenergy follow an exponential distribution, with time constants significantly\ndifferent in the two spectral states. In the soft state of the source a shot\nwith a very large strength has been identified and it has exponential rise and\ndecay phases with time constants of 0.4 s. We examine these results in the\nlight of the current models for accretion onto black holes.\n