Michiel van der Klis

TL;DR: In this paper, the authors reported the discovery of a millisecond radio pulsar in the persistent flux of an X-ray binary system, confirming theoretical expectations, but without direct proof.

TL;DR: In this article, the authors compared the properties of the Z sources with the predictions of the magnetospheric beat-frequency and Lense-Thirring precession models, and showed that the change in the slope of the correlation between the frequency of the horizontal-branch oscillation and the frequency when the latter is greater than 850 Hz is directly related to the varying frequency separation of the kilohertz QPOs.

TL;DR: In this paper, the frequency separation of the quasi-periodic oscillations in the pair appears to be constant in many sources and directly related to the neutron star spin frequency, however, in Sco X-1 and possibly in 4U 1608-52, frequency separation between the QPO peaks decreases with increasing inferred mass accretion rate.

TL;DR: In this article, the Rossi X-ray Timing Explorer was used to detect two simultaneous kHz quasi-periodic oscillations (QPOs) in the bright low-mass Xray binary and Z source GX 5-1.

TL;DR: In this paper, the authors compared positions on a spectral color-color diagram from 10 black hole candidates (BHCs) observed with Ginga with the observed broadband noise (BBN) and quasi-periodic oscillation (QPO) variability, and found that the "very high state" is spectrally intermediate to the soft/high state and hard/low state.