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Preprint 13b/99

The 1999 Her X-1 Anomalous Low State

W. Coburn (1), D. E. Gruber (1), W. A. Heindl (1), M. R. Pelling (1), R. E. Rothschild (1), R. Staubert (2), I. Kreykenbohm (2), P. Risse (2), J. Wilms (2)

(1) Center for Astrophysics and Space Sciences, University of California at San Diego, La Jolla, CA, 92093-0424, USA
(2) Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Waldhäuser Str. 64, D-72076 Tübingen, Germany

To appear in: Proc. of the 5th Compton Symposium, ed. M. McConnell

Abstract. Recently an Anomalous Low State in the 35d cycle of Her X-1, which is thought to be caused by the tilted accretion disk, was observed with the RXTE. This has been seen only twice before; in 1983 and again 1993. We present timing and spectral results of this latest anomalous low obtained 1999 April 26. Pulsations were observed in the 2-20 keV band but with a pulsed fraction down by a factor of 10 from the main-on. Spectral analysis indicates 70% absorbed flux (N_H = 7x10²³ ) with the remainder unabsorbed. This is consistent with continuous screening of the X-ray source by the accretion disk causing the anomalous low.

Key words: -

Paper (76k gzip'ed Postscript including figures)

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