Hercules X-1 Extended Low State

W. Coburn, D. E. Gruber, W. A. Heindl, M. R. Pelling, R. E. Rothschild

R. Staubert, P. Risse, J. Wilms, I. Kreykenbohm


Recently a failed high state turn-on in the 35d cycle of Her X-1, which is thought to be caused by the precession of a 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 extended low obtained 1999 April 26. Pulsations were observed in the 2-20keV band but with a small pulse fraction. Preliminary spectral analysis indicates 70% absorbed emission (NH = 7×1023) with the remainder unabsorbed. This is consistent with a swelling of the accretion disk causing the extended low.

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On 16 Jul 1999, 09:19.