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Institut für Astronomie und Astrophysik

Abteilung Astronomie

Sand 1, D-72076 Tübingen, Germany

Preprint 17c/97

The Physical Interpretation of X-ray Phase Lags and Coherence: RXTE Observations of Cygnus X-1 as a Case Study

M.A. Nowak (1), J.B. Dove (2), B.A. Vaughan (3), J. Wilms (4), and M.C. Begelman (1)

(1) JILA, University of Colorado and the National Institue of Standards and Technology, Campus Box 440, Boulder, CO 80309, USA
(2) Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071, USA
(3) Space Radiation Laboratory, California Institute of Technology, 220-47 Downs, Pasadena, CA 91125
(4) Institut für Astronomie und Astrophysik, Abt. Astronomie, Waldhäuser Str. 64, D-72076 Tübingen, Germany

Contribution to The Active X-ray Sky: Results from Beppo-SAX and RXTE (L. Scarsi, H. Bradt, P. Giommi, F. Fiore, eds.), Nucl. Phys. B, Proc. Suppl.

Abstract. There have been a number of recent spectral models that have met with great success in reproducing the observed X-ray spectra of galactic black hole candidates (GBHC). However, there still exists controversy over such issues as: what are the sources of hard radiation, what is the system's geometry, is the accretion efficient or inefficient, etc. A potentially powerful tool for distinguishing among these possibilities, made possible by the Rossi X-ray Timing Explorer (RXTE), is the variability data. Specifically, here we discuss the implications of the observed phase lags and variability coherence. These data, in conjunction with spectral modelling, have the potential of determining physical sizes of the system, as well as placing strong constraints on both Compton corona and advection models. As an example, we present RXTE variability data of Cyg X-1.

Paper (80k gzip'ed Postscript including figures)

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Jürgen Barnstedt (barnstedt AT astro.uni-tuebingen.de)
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