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The Seyfert 1 galaxy NGC 4593 - I. Variability of the UV spectrum andphysical conditions in the broad line emitting region.
Penston, M. V.; Clavel, J.; Bergeron, J. +2 more
Results obtained for UV observations of NGC 4593 are reported. The observations were carried out at two epochs using the low resolution spectrograph and the large apertures of the IUE satellite. The data reduction is presented. The properties of the UV continuum as well as its variability are investigated, discussing the selection of continuum win…
Further ultraviolet observations of interstellar gas associated with the supernova remnant S 147.
Gondhalekar, P. M.; Phillips, A. P.
The IUE satellite was used to obtain high-resolution ultraviolet observations of the star HD 37318 (B0.5Ve) which lies behind the supernova remnant S 147. High-velocity interstellar absorption lines (>VLSR< ≅ + 80 km s-1) were detected which originate in gas associated with the remnant. These lines have been analysed to…
HZ Her: the nature and origin of the emission lines.
Howarth, I. D.; Wilson, B.
The line spectrum of HZ Her/Her X-1 is investigated in highand low-dispersion IUE spectroscopy. It is noted that while velocity considerations discredit the classical sites of mission, which are the primary star's X-ray heated photosphere, accretion stream, and disk, they support an origin in discrete blobs of material orbiting at the rim of the a…
IUE observations of X-ray selected Seyfert galaxies.
Willis, A. J.; Wilson, R.; Barr, P.
Results are presented for 1150-3150 A spectrophotometry of six type I Seyfert galaxies - NGC 5548, Markarian 79, Markarian 279, Markarian 506, Markarian 376, and 3C 390.3. It is found that the continuous flux distribution can be represented by a single power law in four of these objects, with spectral indices between + 0.2 and - 3.1, while NGC 554…
The conspicuous absence of normal graphite grains in the Small Magellanic Cloud.
Bromage, G. E.; Nandy, K.
The simplest dust model that accurately predicts the normal Galactic interstellar extinction, also fits the normal SMC curve derived from visible and IUE observations. Only one parameter value is different: the usual graphite contribution is at least a factor of 7 weaker in the SMC. Some possible explanations are discussed.
Zinc as a tracer of metallicity in the interstellar medium.
Bromage, G. E.; Blades, J. C.; Harris, A. W.
The relative gas-phase abundance of zinc in the interstellar medium has been studied using high-resolution spectra from the IUE data bank of early-type stars with distances of up to 3 kpc. The chosen sight-lines all have measured N(H) values derived from Copernicus observations. Results show that in the H column density range of 5×1019 …
Ultraviolet spectroscopy of LSI +61 303.
Howarth, I. D.
New IUE low-resolution spectroscopy of the X-ray/radio source LSI+61°303 is presented and discussed, and previously reported data critically reassessed. There is no strong evidence for continuum variability; in particular, eight spectra covering the 1200-1950 Å region show a scatter of only ≡3 per cent. There is some variability in the emission li…
Three low-redshift quasars with absorption systems: IUE andoptical observations.
Kunth, D.; Bergeron, J.
The authors have discovered the first two cases of narrow absorption systems with an absorption redshift equal to the emission redshift (Δv ⪉ 500 km s-1) in the low-redshift quasars PKS 1912-54 (zem = 0.401) and PKS 2135-14 (zem = 0.200). They also confirm the existence of a sharp absorption system (zab …
The Seyfert 1 galaxy NGC 4593- II. The pattern of variability of theUV spectrum.
Clavel, J.
IUE observations of NGC 4593 are found to show approximately 30 percent variations in the intensities of the emission lines and UV continuum in nine days, which set upper limits to the dimension of the UV continuum and broad line emitting regions comparable to that found for NGC 4151 and 3783. UV observations at six different epochs show the exist…
Optical and ultraviolet line profiles and ultraviolet line intensities in the T Tauri star LHα 332-21.
Penston, M. V.; Lago, M. T. V. T.
The ultraviolet spectrum of the T Tauri star LHα 332-21 is presented. This shows emission lines of chromospheric origin. Optical and ultraviolet line profiles for this star are compared: in LHα 332-21 the Mg II lines show blue-displaced absorption and outflow is therefore demonstrated. It is argued that the general similarities of the Mg II line p…