Chaos and random processes in the x ray variability of Cygnus X-1

Miscellaneous · Sun Jan 01 00:00:00 EST 1989

OSTI ID:6032899

Lochner, J C

The temporal variability of the x ray emission of the black hole candidate Cygnus X-1 was examined in an attempt to better characterize the source of the aperiodic variability. The emission is generally believed to come from a turbulent accretion disk surrounding the black hole. Two analysis techniques were applied to low energy x ray light curves: a search for a low-dimensional chaotic attractor; and a new technique to further develop the standard shot noise model. The search for a low-dimensional attractor tests the hypothesis that deterministic chaotic dynamics underlie the accretion disk physics. Using a standard time delay embedding, the phase space trajectory was constructed from the light curve, and the correlation integral was used to determine the dimension of the resulting manifold. The difficulties encountered by this method were investigated with a finite number of data points and a noise level not usually encountered in other applications. The data were not found to indicate that a low-dimensional attractor underlies the variability. This implies that the turbulence in the disk is well developed, and that simple models cannot reliably reconstruct the temporal variability. Shot noise models have long been used as phenomenological, stochastic models for the variability of Cygnus X-1, relying on random pulses of emission, each having a fixed shape and duration. A distribution of shot lengths from 0.01 s to 6.0 s was introduced to reproduce the power density spectrum of the data. The shot profile and the fraction of the emission are found by fitting the phase portrait of the data with trial shot models. Both sets of data are found to be consistent with shots having a symmetric exponential rise and decay, and with the shot amplitude as a power law function of the shot length. These results are interpreted in terms of a distribution of magnetic flares in the disk.

• Research Organization: Maryland Univ., College Park, MD (USA)
• OSTI ID: 6032899
• Resource Relation: Other Information: Ph.D. Thesis
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BLACK HOLES
MATHEMATICAL MODELS
NOISE
X RADIATION
ACCRETION DISKS
BINARY STARS
COSMOLOGICAL MODELS
THEORETICAL DATA
TURBULENCE
DATA
ELECTROMAGNETIC RADIATION
INFORMATION
IONIZING RADIATIONS
NUMERICAL DATA
RADIATIONS
STARS
640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar
Radio & X-Ray Sources