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Institut für Astronomie und Astrophysik

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Preprint 02c/02

Cygnus X-1 from 1998 to 2001: Power Spectra & More

K. Pottschmidt (1), J. Wilms (1), M.A. Nowak (2), G.G. Pooley (3), T. Gleissner (1), W.A. Heindl (4), D.M. Smith (5), R. Remillard (2), R. Staubert (1)

(1) Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Sand 1, D-72076 Tübingen, Germany
(2) Center for Space Research, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, U.S.A.
(3) Astrophysics Group, Cavendish Laboratory, Madingley Road, Cambridge CB3 OHE, England
(4) Center for Astronomy and Space Sciences, Code 0424, University of California at San Diego, La Jolla, CA 92093, U.S.A.
(5) Space Sciences Laboratory, University of California at Berkeley, Berkeley, CA 94720, U.S.A.

in: New Visions of the X-ray Universe in the XMM-Newton and Chandra Era, eds. F. Jansen & TBD, ESA SP-488, 2002


We present the long term evolution of the power spectrum of the black hole candidate Cygnus X-1 in the 0.002-128 Hz frequency range as monitored from 1998 to 2001 with the Rossi X-ray Timing Explorer (RXTE). Following Nowak (2000), we performed multi-Lorentzian fits for all PSDs, selecting the 2-13.1 keV range. We find that in 1998 the total fractional rms amplitude decreases from 36 ± 1% to 29 ± 1%. Unusually many count rate flares have been observed since that time which - like the 1998 July event - can be classified as "failed state transitions", while data taken in 2001 October reveal the first soft state with quenched radio emission of Cyg X-1 since 1996.

Key words: stars: individual: Cyg X-1 - stars: binaries: close - X-rays: stars

Paper (190k gzip'ed Postscript including figures)

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