The ABC of Low-Frequency Quasi-periodic Oscillations in Black Hole Candidates: Analogies with Z Sources

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© 2005. The American Astronomical Society. All rights reserved. Printed in U.S.A.
, , Citation P. Casella et al 2005 ApJ 629 403 DOI 10.1086/431174

0004-637X/629/1/403

Abstract

Three main types of low-frequency quasi-periodic oscillations (LFQPOs) have been observed in black hole candidates. We reanalyzed RXTE data of the bright systems XTE J1859+226, XTE J1550-564, and GX 339-4, which show all three types. We review the main properties of these LFQPOs and show that they follow a well-defined correlation in a fractional rms versus softness diagram. We show that the frequency behavior through this correlation presents clear analogies with that of horizontal-, normal-, and flaring-branch oscillations in Z sources, with the inverse of the fractional rms being the equivalent of the curvilinear coordinate Sz through the Z track.

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10.1086/431174