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Discovery of Submillisecond Quasi-Periodic Oscillations in the X-Ray Flux of Scorpius X-1

van der Klis, M. and Swank, J. H. and Jahoda, K. and Morgan, E. H. and Lewin, W. H. G. and Vaughan, B. and van Paradijs, J. (1996) Discovery of Submillisecond Quasi-Periodic Oscillations in the X-Ray Flux of Scorpius X-1. Astrophysical Journal Letters, 469 (1). L1-L4. ISSN 2041-8205.

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We report the discovery, with NASA's Rossi X-Ray Timing Explorer (RXTE), of the first submillisecond oscillations found in a celestial X-ray source. The quasi-periodic oscillations (QPOs) come from Sco X-1 and have a frequency of ~1100 Hz and amplitudes of 0.6%-1.2% (rms) and are relatively coherent, with Q up to ~102. The frequency of the QPOs increases with accretion rate, rising from 1050 to 1130 Hz when the source moves from top to bottom along the normal branch in the X-ray color-color diagram, and shows a strong, approximately linear correlation with the frequency of the well-known 6-20 Hz normal/flaring-branch QPOs. We also report the discovery of QPOs with a frequency near 800 Hz that occur, simultaneously with the 1100 Hz QPOs, in the upper normal branch. We discuss several possible interpretations, one involving a millisecond X-ray pulsar whose pulses we see reflected off accretion flow inhomogeneities. Finally, we report the discovery of ~45 Hz QPOs, most prominent in the middle of the normal branch, which might be magnetospheric beat-frequency QPOs.

Item Type:Article
Related URLs:
URLURL TypeDescription
van der Klis, M.0000-0003-0070-9872
Swank, J. H.0000-0001-7079-9338
Additional Information:© 1996. The American Astronomical Society. Received 1996 April 25, accepted for publication 1996 July 5. This work was supported in part by the Netherlands Organization for Scientific Research (NWO) under grant PGS 78-277 and by the Netherlands Foundation for Research in Astronomy (ASTRON) under grant 781-76-017. W. H. G. L. and J. v. P. acknowledge support from the National Aeronautics and Space Administration.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Netherlands Organization for Scientific Research (NWO)PGS 78-277
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Space Radiation Laboratory1997-49
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Record Number:CaltechAUTHORS:20141203-110212878
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:52325
Deposited By: Deborah Miles
Deposited On:03 Dec 2014 20:27
Last Modified:09 Mar 2020 13:19

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