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Evidence for rotationally modulated variability in O star winds.
Prinja, Raman K.
The nature of variability observed in the UV resonance line P Cygni profiles of four O stars is interpreted in terms of recurrent episodes of low-velocity broad absorption enhancements evolving into high-velocity narrow absorption components. Profile fitting techniques are used to determine the central velocities of the (multiple) features. The re…
Variability of the soft excess in the Seyfert I galaxy MKN 335.
Turner, T. J.; Pounds, K. A.
The luminous Seyfert I galaxy Mkn 335 was observed by EXOSAT on six occasions between 1983 November 5 and 1985 December 24. A previous analysis of the 1984 December 6 observation revealed a two-component spectrum, with a hard power law dominant above ~2 keV on which was superimposed a strong soft X-ray excess in the 0.1-2 keV band of the EXOSAT lo…
The discovery of orbital dips in the soft X-ray emission of U GEM during an outburst.
King, A. R.; Watson, M. G.; Mason, K. O. +1 more
A series of Exosat and IUE observations of the dwarf nova U Geminorum have been made during the decline from an unusually long outburst that occurred in 1985 October and November. A strong soft X-ray flux was recorded which is modulated with the orbital period of the binary. The modulation takes the form of broad, deep dips whose morphology change…
X-ray observations of the 50-min dipping source XB 1916-053.
Mason, Keith O.; Smale, Alan P.; White, Nick E. +1 more
Three EXOSAT observations of the low-mass X-ray binary XB 1916-053 have revealed extreme variability in the appearance of the dips, ranging from complete absence to two broad, deep dips per 50-min cycle. These dips are believed to result from the obscuration of the central X-ray source by azimuthal structure in the accretion disc. The X-ray spectr…
X-ray and ultraviolet observations of Markarian 421.
Bromage, G. E.; Warwick, R. S.; George, I. M.
We present the results of a detailed study of the BL Lacertae type object Markarian 421 (Mrk 421) based upon EXOSAT and IUE observations made during 1984 and 1985. In the X-ray band Mrk 421 exhibits significant variability on time-scales typically of the order of a day with a minimum e-folding time-scale, t_v_, of ~5x10^4^s. There is some indicati…
Far-ultraviolet absorption lines in active galaxies.
Ulrich, M. -H.
Attention is drawn to the far-ultraviolet absorption lines which have been discovered with IUE in a number of active nuclei. The properties of these lines are presented and discussed with emphasis on the following points: (i) the frequency of occurrence of far ultraviolet absorption lines (ii) a comparison between the properties of these lines and…
EXOSAT observations of variable coronal X-ray emission from the youngK dwarf AB Doradus (= HD 36705).
White, N. E.; Collier Cameron, A.; Bedford, D. K. +2 more
We present the results of a search for rotationally-modulated X-ray emission from the young KO dwarf AB Doradus, using the low- and medium-energy detectors on board the EXOSAT spacecraft. Two sets of observations were obtained, each covering all or nearly all of the 0.514 day rotation period of the star, in 1984 December and 1986 January. A single…
Spectral energy distributions of galaxies in high-redshift clusters. III. Abell 370 at z=0.37.
Ellis, Richard S.; Couch, Warrick J.; MacLaren, Iain
We have imaged the distant cluster Abell 370 (z=0.37) with a CCD- based intermediate pass-band multicolour system defined in earlier papers in this series. Our technique is to use such colours to classify faint galaxies in redshift and spectral class without recourse to spectroscopic data. We demonstrate from a new comparison of ~80 spectra gather…
Very extended ionized gas in radio galaxies - IV. PKS 2152-69.
Snijders, M. A. J.; di Serego Alighieri, S.; Fosbury, R. A. E. +5 more
Optical, radio and ultraviolet observations of the luminous southern radio elliptical galaxy PKS 2152-69 are presented. Narrow-band images and long-slit spectra reveal a system of low-ionization filaments extending out to a maximum radius of 20 arcsec (16kpc; H_0_=50 km s^-1_ Mpc^-1^ as used throughout this paper). To the north-east, however, a lu…
Observational evidence for mass loss from classical cepheids.
Deasy, H. P.
This paper examines the evidence for mass loss from classical Cepheid variables in the light of recent observational studies of infrared and ultraviolet emission from these objects. Mass-loss rates derived for several stars range between 10-10M_sun;yr-1 and 10-6M_sun;yr-1. The lower end of this range pro…