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Preprint 12/00


K. Pottschmidt (1), J. Wilms (1), R. Staubert (1), M.A. Nowak (2), W.A. Heindl (3), and D.M. Smith (4)

(1) Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Waldhäuser Str. 64, D-72076 Tübingen, Germany
(2) JILA, University of Colorado, Boulder, CO 80309-440, USA
(3) CASS, University of California San Diego, La Jolla, CA 92093, USA
(4) SSL, University of California Berkeley, Berkeley, CA 94720, USA

To appear in: Proc. 33rd COSPAR Scientific Assembly (B. Czerny, ed.), Adv. Space Res.

Abstract. We present temporal and spectral results from monitoring Cygnus X-1 with the Rossi X-ray Timing Explorer (RXTE) in 1998 and 1999. We concentrate on the long term evolution of the hard state timing properties, comparing it to the 1996 soft state evolution. This leads to the following results: 1. the hard and soft state time lag spectra are very similar, 2. during state transitions, the lags in the 1-10 Hz range increase by more than an order of magnitude, 3. in the hard state itself, events can be seen - the temporal and spectral evolution during the of 1998 July identifies it as a "failed state transition". During (failed) state transitions, the time lag spectra and the power spectra change predominantly in the 1-10 Hz range. We suggest that this additional variability is produced in ejected coronal material disrupting the synchrotron radiation emitting out present in the hard state.

Key words: -

Paper (121k gzip'ed Postscript including figures)

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