Search Publications
Luminosity Effects and the Emission-Line Properties of Quasars with 0 < Z < 3.8
Green, Richard F.; Osmer, Patrick S.; Porter, Alain C.
We present data and a spectral atlas for 76 quasars with 2.97 < z < 3.80 and for 33 quasars with z ~ 2, together with measures of 73 quasars from the IUE archives that mostly have z < 1. The quasars provide a sampling of the luminosity-redshift plane at constant luminosity for 0 < z < 3.8, a range of a factor of 40 in luminosity for…
The Morphology of Faint Galaxies in Medium Deep Survey Images Using WFPC2
Glazebrook, K.; Illingworth, G. D.; Koo, D. C. +12 more
First results from HST Medium Deep Survey images taken with WFPC2 demonstrate that galaxy classifications can be reliably performed to magnitudes I_814_ <~ 22.0 in the F815W band. Published spectroscopic surveys to this depth indicate a mean redshift of z^bar^ ~ 0.5. We have classified over 200 galaxies in nine WFPC2 fields according to a basic…
HST-GHRS observations of β Pictoris: additional evidence for infalling comets
Deleuil, M.; Feldman, P. D.; Moos, H. W. +9 more
Variable redshifted absorption features observed in the spectrum of β Pictoris have been attributed to comet-like bodies falling towards the star. The high quality data obtained in December 1992 at the unprecedented resolution and sensitivity of the GHRS reinforces the model that both the changes in spectral line shapes as well as the very presenc…
Spectral and correlated timing behaviour of GX5-1.
van Paradijs, J.; van der Klis, M.; Lewin, W. H. G. +4 more
We have analyzed the X-ray spectral and fast timing behaviour of the Z-source GX5-1 using X-ray colour-colour diagrams (CDs), hardness-intensity diagrams (HIDs) and power spectra. We used all EXOSAT ME data on GX5-1, a total of seven observations during 1983-1985. We detect, for the first time in GX5-1, secular motion of the well known "Z" pattern…
Is there primordial gas in IZw 18 ?
Kunth, D.; Sargent, W. L. W.; Lequeux, J. +1 more
The dwarf emission line galaxy IZw 18 has one of the lowest known O/H abundance ratios (O/H = 1.75 10^-5^) deduced from its emission lines. Its two main emission patches are associated with two extended HI clouds with very high column densities (N(HI) = 10^22^ H atoms cm^-2^). We have obtained spectra of the northwest emission region with the GHRS…
HST/FOC Imaging of the Narrow-Line Region of NGC 1068
Boksenberg, A.; Capetti, A.; Sparks, W. B. +2 more
We present imaging observations of NGC 1068 taken with the COSTAR- corrected (Corrective-Optics Space Telescope Axial Replacement) Faint Object Camera on board the Hubble Space Telescope in the UV and optical continuum and [O III] emission lines. From these observations the structure of the nuclear region of NGC 1068 is shown to be very complex. B…
Temperatures and luminosities of symbiotic novae.
Murset, Urs; Nussbaumer, Harry
Symbiotic novae occur in double star systems, where mass lost by a red giant is accumulated by wind accretion onto a wite dwarf. When a critical mass has been reached, a nova-like outburst of long duration sets in, the outbursts lasts many dozons of years. We determine the evolution of luminosity and temperature during the outburst. We find slowly…
The relationship between interplanetary discontinuities and Alfvén waves: Ulysses observations
Balogh, A.; Tsurutani, B. T.; Smith, E. J. +7 more
The rate of occurrence of interplanetary discontinuities (ROID) is examined using Ulysses magnetic field and plasma data from 1 to 5 AU radial distance from the Sun and at high heliographic latitudes. We find two regions where the ROID is high: in stream-stream interaction regions and in Alfvén wave trains. This latter feature is particularly obvi…
New Images of the Distant, Rich Cluster CL 0939+4713 with WFPC2
Lucas, Ray A.; Sparks, William B.; Dressler, Alan +1 more
New images of the distant cluster of galaxies CL 0939+4713 at z = 0.41 have been taken with the WFPC2 on the HST. The images go deeper and show considerably more detail than the aberrated images from WFPC1. We confirm that for this cluster the Butcher-Oemler effect results from a surprisingly large population of late-type spiral and irregular gala…
A study of the luminous blue variable candidate He 3-519 and its surrounding nebula.
Crowther, P. A.; Smith, L. J.; Prinja, R. K.
He 3-519 is 20 min away from the well-known Luminous Blue Variable (LBV) AG Car and is surrounded by a ring nebula 1 min diameter. In this paper, we present the first detailed study of He 3-519 and its surrounding nebula based on high resolution spectra obtained at the Anglo-Australian Telescope (AAT) with the University College London (UCL) echel…