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Bimodal quasi-oscillatory and spectral behavior in Sco X-1X-ray observations were made to follow up the discovery of quasi-periodic oscillations (QPO) in Sco X-1. The QPO is observed in the quiescent state, and between flares in the active state. When the source is quiescent, the QPO frequency is 6 Hz and anticorrelated with intensity; in the active state, the frequency ranges from 10 to 20 Hz and is strongly correlated with intensity. At high intensities the QPO dissolves into continuum noise. The QPO rms amplitude decreases with count rate, and increases with photon energy. There are two modes of spectral behavior, with a one-to-one correspondence to the two modes of QPO: the spectral hardness ratio varies more steeply with intensity when the source shows 6 Hz QPO, than for 10 to 20 Hz QPO. Transitions between QPO modes, which occur when the flux is at its lowest levels, correspond to transitions between hardness ratio modes. The QPO frequency changes continuously through the transitions, which last a few hundred seconds.
Document ID
19870002229
Acquisition Source
Legacy CDMS
Document Type
Preprint (Draft being sent to journal)
Authors
Priedhorsky, W.
(Max-Planck-Inst. fuer Physik und Astrophysik Garching, Germany)
Hasinger, G.
(Max-Planck-Inst. fuer Physik und Astrophysik Garching, Germany)
Lewin, W. H. G.
(Max-Planck-Inst. fuer Physik und Astrophysik Garching, Germany)
Middleditch, J.
(Max-Planck-Inst. fuer Physik und Astrophysik Garching, Germany)
Parmar, A.
(Max-Planck-Inst. fuer Physik und Astrophysik Garching, Germany)
Stella, L.
(Max-Planck-Inst. fuer Physik und Astrophysik Garching, Germany)
White, N.
(Max-Planck-Inst. fuer Physik und Astrophysik Garching, Germany)
Date Acquired
August 13, 2013
Publication Date
January 1, 1985
Publication Information
ISSN: 0178-0719
Subject Category
Astrophysics
Report/Patent Number
MPE-PREPRINT-45
Accession Number
87N11662
Distribution Limits
Public
Copyright
Other

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