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The galactic ridge observed by Exosat
Warwick, R. S.; Watson, M. G.; Turner, M. J. L. +1 more
We have used Exosat to map the distribution of X-ray emission in the galactic plane. In addition to numerous point sources, the map reveals a narrow continuous ridge of emission which extends along the galactic plane either side of the galactic centre out to ~40° longitude. The origin of this feature remains uncertain although a major contribution…
An extended X-ray low state from Hercules X-1
Pietsch, W.; Parmar, A. N.; White, N. E. +4 more
Hercules X-1 exhibits a 35-day cycle in its X-ray intensity1,2 in addition to its pulsar rotational and orbital periodicities of 1.24 s and 1.7 days respectively. The effects of X-ray heating on the companion are visible throughout the 35-day cycle3, suggesting that the observed intensity modulation is caused by periodic bloc…
Transient quasi-periodic oscillations in in the X-ray flux of Cygnus X-3
van der Klis, M.; Jansen, F. A.
Cygnus X-3, a bright X-ray source at a distance1 of more than ~12 kpc beyond the edge of the galactic plane, has peculiar properties including very strong radio outbursts2, possibly showing jet-like features3, and emission in various γ-ray bands4-6 (but see ref. 7). The discovery of its 4.8-h X-ray perio…
Ultraviolet continuum variability of the quasar 3C273
Ulrich, M. H.; Courvoisier, T. J. -L.
Several quasars show an excess of radiation in the ultraviolet over the power law defined by their infrared/optical continuum. Several authors1-4 have fitted the infrared to ultraviolet spectrum of these quasars with a combination of a power law component, line emission, blends of Fe II lines, Balmer continuum and a black-body component…
An X-ray corona in SS Cygni?
Heise, J.; King, A. R.; Watson, M. G.
A recent model1 for the X-ray emission of non-magnetic cataclysmic variables suggests that most of the observed hard X-ray flux originates in a radiatively-cooling quasi-hydrostatic corona surrounding the white dwarf as it accretes from its companion. We present here some results from a ~7.5-h EXOSAT observation of the dwarf nova SS Cyg…
EXOSAT observations of a 2,000-s intensity dip in Seyfert galaxy NGC4151
Cruise, A. M.; Whitehouse, D. R.
Variations in the flux from active galactic nuclei (AGN) allow the testing of models of their emission mechanisms. Various suggestions for the energy generation in AGNs require the existence of a compact object, with X rays generated deep in that object's potential well and, therefore, X-ray luminosity related directly to the object responsible fo…