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GX 349+2 (Sco X-2): An odd-ball among the Z sources
Erik Kuulkers, Michiel van der Klis
We report on about 4 hrs of observations made with the Rossi X-ray Timing Explorer on 1997 May 2 of the low-mass X-ray binary and Z source GX 349+2 (Sco X-2). Initially the source…
Absorption dips in GRO J1655-40: mapping the inner accretion disk
Erik Kuulkers, Rudy Wijnands, Tomaso Belloni +3
Using the RXTE PCA we discovered dips in the X-ray light curves of the black-hole candidate GRO J1655-40 during outburst. They are short (~minute) and deep (down to ~8% of the out-…
The mass of the neutron star in Cyg X-2 (V1341 Cyg)
Jorge Casares, Phil Charles, Erik Kuulkers
Cygnus X-2 is one of the brightest and longest known X-ray sources. We present high resolution optical spectroscopy of Cyg X-2 obtained over 4 years which gives an improved mass fu…
Discovery of KiloHertz Quasi-Periodic Oscillations in the Z source Cygnus X-2
Rudy Wijnands, Jeroen Homan, Michiel van der Klis +6
During observations with RXTE we discovered two simultaneous kHz QPOs near 500 Hz and 860 Hz in the Z source Cyg X-2. In the X-ray color-color diagram and hardness-intensity diagra…
Absorption dips in the light curves of GRO J1655-40 and 4U 1630-47 during outburst
Erik Kuulkers, Rudy Wijnands, Tomaso Belloni +3
Using the RXTE PCA we discovered deep dips in the X-ray light curves of the black-hole candidates GRO J1655-40 and 4U 1630-47 during outburst. Similar kind of dips for GRO J1655-40…
KiloHertz Quasi-Periodic Oscillations in GX 17+2
Rudy Wijnands, Jeroen Homan, Michiel van der Klis +7
We observed the low-mass X-ray binary and Z source GX 17+2 with the Rossi X-ray Timing Explorer during 6-8 Feb 1997, 1-4 Apr 1997, and 26-27 Jul 1997. The X-ray color-color diagram…
Kilohertz QPO and Atoll Source States in 4U 0614+09
M. Mendez, M. van der Klis, J. van Paradijs +5
We report three RXTE/PCA observations of the low-mass X-ray binary 4U 0614+09. They show strong (~ 30% rms) band-limited noise with a cut-off frequency varying between 0.7 and 15 H…
Discovery of microsecond time lags in kilohertz QPO
Brian A. Vaughan, Michiel van der Klis, Mariano Mendez +7
Using the Rossi X-ray Timing Explorer we have measured 27 microsecond time delays in 830 Hz quasi-periodic oscillations (QPO) between 4-6 keV and 11-17 keV in 4U 1608-52, with high…
Ginga observations of Cygnus X-2
R. A. D. Wijnands, M. van der Klis, E. Kuulkers +2
We analysed all X-ray data on the low-mass X-ray binary Cygnus X-2 obtained with Ginga. The analysis of the spectral and fast timing behaviour of these 4 years of data provides new…
GX 17+2: X-ray spectral and timing behaviour of a bursting Z source
E. Kuulkers, M. van der Klis, T. Oosterbroek +2
We investigated the properties of the Z pattern of the low-mass X-ray binary GX 17+2 in the X-ray colour-colour diagrams (CDs) and hardness-intensity diagrams (HIDs), and of the po…