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A varying kHz peak separation in 4U 1608-52

M. Mendez·M. van der Klis·J. van Paradijs·W. H. G. Lewin·B. A. Vaughan·E. Kuulkers·W. Zhang·F. K. Lamb·D. Psaltis
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Abstract

Using a new technique to improve the sensitivity to weak Quasi-Periodic Oscillations (QPO) we discovered a new QPO peak at about 1100 Hz in the March 1996 outburst observations of 4U 1608-52, simultaneous with the ~ 600-900 Hz peak previously reported from these data. The frequency separation between the upper and the lower QPO peak varied significantly from $232.7 \pm 11.5$ Hz on March 3, to $293.1 \pm 6.6$ Hz on March 6. This is the first case of a variable kHz peak separation in an atoll source.

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M. Mendez, M. van der Klis, J. van Paradijs, W. H. G. Lewin, B. A. Vaughan, E. Kuulkers, W. Zhang, F. K. Lamb, D. Psaltis. 1997-12-10. A varying kHz peak separation in 4U 1608-52. https://doi.org/10.1063/1.55922

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