Search Publications
The ultraviolet continuum of quasars -I. The shape of the continuum, continuum reddening and intervening absorption.
Wilson, R.; Gondhalekar, P. M.; Obrien, P. T.
We present ultraviolet data for a sample of 81 quasars covering a wide redshift and luminosity range. After allowing for the effect of absorption due to intervening clouds, the intrinsic optical and ultraviolet continuum for quasars is found to steepen towards shorter wavelengths from ~ 1 micron to ~800 A by ~1 in spectral index. The mean ratio of…
An accretion disc in the broad-line radio galaxy 3C 390.3 ?
Penston, M. V.; Perez, E.; Moles, M. +2 more
The permitted broad component of the Hβ emission line in the broadline radio galaxy (BLRG) 3C390.3 presents a double-peaked structure, similar to that seen in cataclysmic variables. The profile of the line is well fitted by a relativistic accretion disc with an intermediate inclination to the line-of-sight.
The interstellar extinction in the open clusters TR 14, TR 15, TR 16/Cr 232 and CR 228 in NGC 3372 New near-infrared photometry.
Roth, M.; Ruiz, M. T.; Tapia, M. +1 more
Near-infrared JHKL photometry of more than 200 stars, members of the open clusters Tr 14, Tr 15, Tr 16, Cr 228 and Cr 232 in the Carina Nebula are presented. From comparing these results with the available visual photometry and spectroscopy, it is found that, except in Tr 15, the intracluster reddening is characterized by a 'normal' extinction law…
Opacity enhancements in the stellar wind of 68 Cygni - not "shells" or "puffs".
Howarth, Ian D.; Prinja, Raman K.
Results presented from a study of variability in the stellar wind of 68 Cyg [O7.5 III((f))], based on 33 IUE high-resolution spectra taken over ≡7 days in 1986 August. Significant changes are evident in the Si IV resonance line profiles on time-scales as short as ≡1 hr; these changes are characterized by broad low-velocity (≡0.55v) absorption enha…
The 1985 May superoutburst of the dwarf nova OY Carinae - II. IUE andEXOSAT observations.
Sonneborn, G.; van Paradijs, J.; Charles, P. A. +4 more
The authors present ultraviolet (IUE) and X-ray (EXOSAT) observations of the eclipsing dwarf nova OY Carinae during the superoutburst of 1985 May. From the lack of X-ray eclipse and UV behaviour they deduce that the X-ray flux originates in an optically thin corona comparable in size to the Roche lobe, and not directly from the white dwarf or boun…
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…
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 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…
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…