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Correlation between spectral state and quasi-periodic oscillation parameters in GX 5-1In a series of seven Exosat observations, the bimodal spectral behavior and the quasi-periodic oscillation (QPO)/red noise properties of GX 5-1 show a strict correlation. In one of the two spectral states (characterized by a 'horizontal branch' in the hardness-intensity diagram), strong 20-40 Hz QPO and red noise below about 60 Hz were always present. In the other ('normal branch'), no QPO between 6 and 60 Hz or red noise above 1 Hz were detected, but there was an indication for weak QPO near 5 Hz. In both states 'very low frequency noise' (VLFN) is detected below 0.1 Hz which has a power-law shape and and which extends down to the lowest observed frequencies (0.0001 Hz). The VLFN is probably not directly related to the QPO. The results are compared to those on Sco X-1 and Cyg X-2 and it is concluded that, although all three sources show bimodal spectral and QPO/red noise behavior, there is a qualitative difference between GX 5-1 and Cyg X-2 on one hand and Sco X-1 on the other.
Document ID
19870044578
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Van Der Klis, M.
(ESA European Space Science Dept., Noordwijk, Netherlands)
Jansen, F.
(Leiden Rijksuniversiteit, Netherlands)
Van Paradijs, J.
(Amsterdam, Universiteit Netherlands)
Lewin, W. H. G.
(MIT Cambridge, MA, United States)
Sztajno, M.
(Max-Planck-Institut fuer extraterrestrische Physik Garching, Germany)
Date Acquired
August 13, 2013
Publication Date
February 1, 1987
Publication Information
Publication: Astrophysical Journal, Part 2 - Letters to the Editor
Volume: 313
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
87A31852
Funding Number(s)
CONTRACT_GRANT: NAG8-571
Distribution Limits
Public
Copyright
Other

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