Search Publications
Secular variations in the Z source CygnusX-2.
van der Klis, M.; Kuulkers, E.; Vaughan, B. A.
We analyzed the X-ray spectral variations of the low-mass X-ray binary CygX-2 on time scales longer than one day using EXOSAT data. We describe these variations in terms of the shifts and shape changes of the "Z" pattern in X-ray colour-colour and hardness-intensity diagrams. CygX-2 varies between three intensity "levels": "high", "medium" and "lo…
The X-ray and EUV spectrum of the dwarf nova VW Hydri in outburst and quiescence.
Belloni, T.; Verbunt, F.; Watson, M. G. +5 more
We combine ROSAT, Ginga, and EXOSAT observations to investigate the X-ray and extreme-ultraviolet fluxes of VW Hyi in quiescence and throughout an ordinary dwarf-nova outburst. We show that the quiescent spectrum is consistent with emission from material heated to ~12keV and cooling through the X-ray band to temperatures below our sensitivity rang…
DA white dwarfs in pointed observations from the ROSAT archive.
Wolff, B.; Jordan, S.; Koester, D.
87 pointed PSPC (Position Sensitive Proportional Counter) observations of hot DA white dwarfs, available in the ROSAT public archive until the end of 1994, have been analyzed together with Wide Field Camera (WFC) and EXOSAT data. From the 57 objects with a significant count rate half of the objects have a temperature below 38,000K and a virtually …
GX340+0 with EXOSAT: its correlated X-ray spectral and timing behaviour.
van der Klis, M.; Kuulkers, E.
We report on three observations of the Z source GX340+0 performed with EXOSAT during 1985 and 1986. In two observations the source was in the horizontal branch and the upper part of the normal branch of the Z pattern in the X-ray colour-colour diagram, while in the third observation it was in the normal and flaring branches. We found that the hori…
Accretion torques in the transient X-ray pulsar EXO2030+375.
Parmar, A. N.; Verbunt, F.; Wilson, R. B. +4 more
In 1985 May - October, EXOSAT observed two outbursts from the previously unknown accreting X-ray pulsar EXO2030+375. Using the orbital solution derived by the BATSE experiment on CGRO, the behavior of the pulse period variations can now be studied with much less ambiguity than was possible based on the EXOSAT observations alone. There is little ev…
Search for neutron star spin periods in X-ray bursts.
van der Klis, M.; Jongert, H. C.
We report a search for pulsations in 147 Type 1 X-ray bursts observed with EXOSAT in 10 X-ray burst sources. Instead of treating each burst separately, we incoherently averaged the power spectra of all of the bursts of a given burster to improve statistics. No periodicities were detected; 99% confidence upper limits on the modulation depths of pos…
Branches and loops in the X-Ray colour-colour diagram of Cygnus X-3.
van der Klis, M.; Smit, J. M.
We present an analysis of EXOSAT ME X-ray colour-colour diagrams of Cygnus X-3. Our sample contains all the Cygnus X-3 data collected during EXOSAT's operational life time and covers a total of 190 hours. The colour-colour diagrams display X-ray spectral variations with the 4.8 hour period and show the spectral distinction between the `high' and t…