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EXOSAT Medium-Energy Observations of CYGNUS-X-2
Pietsch, W.; Hasinger, G.; Sztajno, M. +1 more
On July 5. 6. 1983, during the EXOSAT performance verification (PV) and calibration phase, a raster scan of Cygnus X-2 was performed. In contrast to the previously observed smooth intensity variations on timescales of hours, the source revealed a behaviour unknown until now: active periods with high energy flares recurring on time scales of 300 50…
Hard X-Ray Observations of the Eclipsing Binary Ex-Hydrae
Beuermann, K.; Osborne, J.
The authors present light curves of EX Hydrae in the 1 - 10 keV range obtained with the medium energy experiment of EXOSAT. The 67-min modulation was observed with a peak-to-peak amplitude of 36% in the 1 - 4 keV range and of 24% in the 4 - 9 keV range. Newly discovered was a partial X-ray eclipse of ≡3 min full width which coincides with the opti…
Temporal Intensity Fluctuations of HERCULES-X-1 around 100-SECOND Timescales
Pietsch, W.; Kahabka, P.; Truemper, J. +2 more
Her X-1 has been observed with EXOSAT for one 35d cycle between March 1 and April 5, 1984 at about 4 day intervals. During three observations, absorption dips were encountered showing fluctuations with time scales in the several hundred seconds range. The data are interpreted with a model where random superposition of absorbing blobs or…
The Big Dipper - 4U1624-49
Halpern, J.; Grindlay, J. E.; King, A. R. +2 more
We present a 6.3 hour observation of 4U1624-49 with the EXOSAT Medium Energy experiment. The X-ray light curve is dominated by a series of sharp dips in which the observed flux falls to ∼25% of the steady level on timescales of seconds. These dips are accompanied by strong variations in the spectral hardness consistent with large changes in the ab…
X-Ray Emission from Isolated Hot White Dwarfs
Heise, J.
Hot white dwarfs are objects that copiously emit in the Extreme Ultraviolet and soft X-ray range. They are the brightest sources seen in the Low Energy Telescope of EXOSAT, with countrates up to 25 cnts/s. in contrast to their optical and UV spectrum the total flux and spectral distribution at soft X-ray energies are highly sensitive to the effect…
EXOSAT observations of the X-ray pulsar 4U1145-619
Warwick, R. S.; Watson, M. G.; Willingale, R.
EXOSAT observations of the X-ray pulsar 4U1145-619 during June and July 1983 and July 1984 confirm that this source shows a regular 187 day outburst cycle in X-rays. The results from pulse timing and X-ray spectroscopy are discussed in terms of a model for 4U1145-619 involving an eccentric binary system in which there is variable accretion from th…
EXOSAT and Optical Observations of the X-Ray Burst Source 4U/MXB1636-53
Pietsch, W.; van Paradijs, J.; van der Klis, M. +5 more
During May 1984 we made a one-day EXOSAT observation of the X-ray burst source 4U/MXB1636-53, partly simultaneous with Tenma and with optical observations at ESO. In this paper we give a short description of the main results: (i) Discovery of a constant blackbody component in the persistent X-ray emission, with an apparent blackbody radius consist…
EXOSAT observations of NGC 1399 and NGC 1404: Two elliptical galaxies in the center of the Fornax cluster
Mason, K. O.; Rosen, S. R.
Imaging X-ray observations of the Fornax cluster of galaxies centered on NGC 1399 and NGC 1404 are presented. NGC 1399 and NGC 1404, which are separated by about 10 arc minutes, are found to have an unusually high ratio of x-ray to optical flux. We consider the possibility that the x-radiation is produced by hot gas in the cores of the galaxies. W…
Study of Rapid Variability in CYGNUS-X-1
Page, C. G.
The EXOSAT Medium Energy instrument has been used with the new HER6 mode to study the rapid variability of Cygnus X-1. It was found that the fluctuations in the higher energy band (5 - 14 keV) lagged behind those in the lower band (2 - 5 keV) by about 6 milliseconds. This confirms predictions of the inverse Compton model and gives an upper limit t…
Observation of an X-Ray Outburst and Quiescent Emission from the Rs-Canum Binary HR1099
Barstow, M. A.
The RS CVn binary HR1099 has been observed with the medium energy (ME) and low energy (LE) experiments on EXOSAT. X-ray emission was detected from two quiescent components with temperatures ∼4.5 × 105K and ∼4 × 107K, which were observed to flare during the observation. The data are compared with models of coronal behaviour. A…