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Institut für Astronomie und Astrophysik

Abteilung Astronomie

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Preprint 11a/97

The 35 day cycle of Her X-1 and the coronal wind model

S. Schandl, R. Staubert, M. König

Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Waldhäuser Str. 64, D-72076 Tübingen, Germany

Contribution to the 4th COMPTON Symposium on Gamma Ray Astronomy and Astrophysics, Williamsburg, Virginia, USA, April 27-30, 1997

Abstract. We present the longterm behaviour of the pulse period and the 35 day precession including historical data as well as new results from GRO/BATSE and the All Sky Monitor onboard RXTE. We find a strong correlation showing shorter precession periods during spin-down phases. Spin-down corresponds to smaller accretion rates (Gosh and Lamb 1979). With reference to the coronal wind model we propose now that the shape of the warped accretion disk depends on the accretion rate. And the precessional period depends on the disk shape. The effect is of the right order to explain the observed correlation.

Paper (46k gzip'ed Postscript including figures)

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