Search Publications
Connection between X-Ray and Optical Variability in NGC 4151
Oknyanskij, V. L.
We have used long light curves in the X-ray (ARIEL V, EXOSAT, Ginga and others), UV (IUE), and optical (data of intensive ground-based monitoring) ranges of NGC 4151 to investigate connections between variations in these spectral fields. Applying Fourier (CLEAN algorithm) and modern cross-correlation analysis, we revealed the different character o…
X-Ray Observations of Gamma-Ray Burst Sources
Hurley, K.; Boer, Michel; Pizzichini, G. +1 more
We report on preliminary results of EXOSAT observations of three gamma-ray burst error boxes. No source was detected down to a limit of 10‑10 erg cm‑2s‑1, assuming a black-body spectrum for the burst counterpart. Results are interpreted in the framework of current theoretical models.
New EXOSAT Observations of Tv-Columbae - Preliminary Results
van der Woerd, H.; Brinkman, A. C.; Schrijver, J.
The first results of the analysis of new EXOSAT observations of the DQ Her type cataclysmic variable TV Col are presented. The period of the 1–10 keV X-ray pulsation associated with the white-dwarf rotation is now established as 1911 s. The pulsations are most pronounced in the lower energy channels (1–3.5 keV). The X-ray light curve shows absorpt…
EXOSAT Observations of H2252-035 - Pulse Phase and Orbital Phase Dependent Low Energy Absorption and Iron Line Emission
Pietsch, W.; Pakull, M.; Kendziorra, E. +1 more
The 805 sec pulsing X-ray source H2252-035 has been observed for 7 h on September 14/15 and on September 17, 1983 in X-rays with the low energy telescope and the medium energy detectors of EXOSAT. While below 2 keV the semiamplitude of the 805 s pulses is ∼100% in the 2.3–7.9 keV band it is only ∼40%. X-ray dips that are more pronounced in low ene…
EXOSAT observations of the ring nebula NGC 6888 and HD 192163
Kaehler, H.; Ule, T.; Wendker, H. J.
A 25 hr exposure of the ring nebula NGC 6888 was obtained with the EXOSAT X-ray Observatory. X-ray emission of the nebula was not found. Taking all instrumental effects and the large nebular area into account, a conservative upper limit of 1×10‑12 erg s‑1 cm‑2 (0.05–2 keV) is derived. This is about an order of magn…
Changes in the Soft and Hard X-Ray Lightcurves of the Am-Herculis Object E:1405-451
Cristiani, S.; Cropper, M.; Osborne, J. P.
The preliminary results of EXOSAT and contemporaneous optical observations of E1405-451 (V834 Cen) in 1985 and 1986 are presented. In the latter of the two observations the soft X-ray light curve was observed to be quite different to that seen in all previous observations, but similar to the optical light curve and the new soft X-ray light curve o…
Low-Mass X-Ray Binaries in the Large Magellanic Cloud
Beuermann, K.; Bianchi, L.; Pakull, M. W. +1 more
We report results on three low-mass X-ray binaries (LMXB) in the LMC, obtained with EXOSAT, IUE and ground-based (ESO) telescopes: LMC X-2 which appears to be "Sco X-1"-like, LHG 83 and LHG 87. The latter are two weaker sources first detected in the course of the HEAO-B LMC survey. They have faint optical counterparts of which LHG 87 was only rece…
X-Ray Emission from Non-Magnetic Cataclysmic Variables
van der Woerd, H.
EXOSAT observations of a large sample of non-magnetic cataclysmic variables have led to the detection of VW Hyi and OY Car as strong soft X-ray sources during superoutburst. The spectral characteristics of the X-ray emission of these SU Uma systems are compared. It is proposed that both systems have, besides a cool, optically thick boundary layer,…
A Simultaneous X-Ray and Optical Study of Tt-Arietis
Stecklum, B.; Toth, I.; Richter, G. A. +21 more
Prelimary results of an extended program of coordinated X-ray and optical observations of TT Ari are presented. The object was observed on August 21/22 1985 both in X-rays (EXOSAT) and optical range, about 100 days after the return to the active state. The first detailed simultaneous study of TT Ari in active state indicates the presence of strong…
X-Ray Observations of Cataclysmic Variables
Osborne, J. P.
The X-ray observatory EXOSAT spent over 1000 hours observing cataclysmic variables. Some of the major results reviewed here are: soft X-ray light curve changes in AM Her objects, orbital effects in the X-ray light curves of intermediate polars and U Gem, regular behaviour in the inter-outburst X-ray flux of VW Hyi, and X-ray emission from the tenu…