Time Domain Studies of X-Ray Shot Noise in Cygnus X-1

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We investigate the variability of Cygnus X-1 in the context of shot noise models, and employ a peak detection algorithm to select individual shots. For a long observation of the low, hard state, the distribution of time intervals between shots is found to be consistent with a purely random process, contrary to previous claims in the literature. The detected shots are fit to several model templates and found to have a broad range of shapes. The fitted shots have a distribution of timescales from below 10 milliseconds to above 1 second. The coherence of the cross spectrum of light curves ... continued below

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Focke, Warren; Wai, Lawrence L.; /SLAC; Swank, Jean H. & /NASA, Goddard July 27, 2005.

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We investigate the variability of Cygnus X-1 in the context of shot noise models, and employ a peak detection algorithm to select individual shots. For a long observation of the low, hard state, the distribution of time intervals between shots is found to be consistent with a purely random process, contrary to previous claims in the literature. The detected shots are fit to several model templates and found to have a broad range of shapes. The fitted shots have a distribution of timescales from below 10 milliseconds to above 1 second. The coherence of the cross spectrum of light curves of these data in different energy bands is also studied. The observed high coherence implies that the transfer function between low and high energy variability is uniform. The uniformity of the transfer function implies that the observed distribution of shot widths cannot have been acquired through Compton scattering. Our results in combination with other results in the literature suggest that shot luminosities are correlated with one another. We discuss how our experimental methodology relates to non-linear models of variability.

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  • Journal Name: Astrophysical Journal; Journal Volume: 633

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  • Report No.: SLAC-PUB-11367
  • Grant Number: AC02-76SF00515
  • Office of Scientific & Technical Information Report Number: 878818
  • Archival Resource Key: ark:/67531/metadc880986

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  • July 27, 2005

Added to The UNT Digital Library

  • Sept. 21, 2016, 2:29 a.m.

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  • Dec. 2, 2016, 3:43 p.m.

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Focke, Warren; Wai, Lawrence L.; /SLAC; Swank, Jean H. & /NASA, Goddard. Time Domain Studies of X-Ray Shot Noise in Cygnus X-1, article, July 27, 2005; [Menlo Park, California]. (digital.library.unt.edu/ark:/67531/metadc880986/: accessed November 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.