Search Publications
Asteroseismology of Planetary Nebula Nuclei
Bond, Howard E.; Ciardullo, Robin; Kawaler, Steven D.
Nine PNNs are now known to be pulsating variables. All of them are OVI or PG1159-type objects, with extreme hydrogen deficiency and high abundances of C and O. They are non-radial pulsators, with typical periods of 10 to 30 min, and their probable descendants are the shorter-period GW Vir (PG) pulsating white dwarfs whose PNe have presumably dispe…
Circumstellar MG II absorption in UV spectra of hot companions of red giants and the meaning of the MG II asymmetry dividing line.
Reimers, D.; Hunsch, M.
High-resolution lUE spectra of the Mg II 2800 Å doublet of 28 red giant/hot main-sequence binary systems have been investigated for circumstellar (wind-) material of the red giant in the line of sight of the hot companion. The aim was to define more clearly a "wind dividing line" by means of Mg II absorption. Special care is taken to determine tem…
The nature of the X-ray spectrum of VW Hydri.
Verbunt, Frank; van Teeseling, Andre; Heise, John
We analyze the EXOSAT data of the October 1984 superoutburst of the dwarf nova VW Hydri. We use the upper limit to the flux at 650 A, measured by VOYAGER, to argue that the spectral component that dominates at 1000 A does not significantly contribute to the counts in any of the EXOSAT filters. This is confirmed by analysis of a flux-ratio diagram,…
Activity in late-type stars. VIII. The nature of the dM(e) or "zero" H-alpha stars.
Byrne, P. B.
We present the results of ultraviolet spectroscopy of three M dwarf stars which, according to Stauffer & Hartmann (1986), have no Hα, either in absorption or emission, in their visible spectra. Using chromospheric and transition region emission line fluxes derived from these spectra, we demonstrate that these stars undergo lower rates of chrom…
HIPPARCOS link with Carte du Ciel triple images.
Tucholke, H. -J.; Brosche, P.; Guibert, J. +3 more
This study for the first time investigates the possibility of deriving astrometric positions for bright stars on Carte du Ciel (CdC) plates, whose triple images are not separable. The field from the Bonn Hipparcos Extragalactic Link Programme with the BL Lac object OJ 287 has been selected. The triple images on the CdC plate were modelled by three…
IUE observations of X-ray nova MUSCAE 1991 during outburst.
Shrader, C. R.; Gonzalez-Riestra, R.
We report on a series of ultraviolet spectroscopic observations made with the lUE satellite, which sampled critical outburst stages of the soft X-ray transient Nova Muscae 1991. Continuum light curves, and multi-epoch line analysis are presented. The λλ1500-3300 continuum fits approximately the "canonical" fv∝ν1/3 power law e…
Extended Variability of the Symbiotic Star AG Draconis
Kafatos, M.; Meier, S. R.; Martin, I.
High and low resolution IUE satellite observations of the symbiotic star AG Draconis covering the period 1979-1989 are presented, and the far-UV spectra are studied. Two extended outburst events are found to have two maxima separated by about 1600 days, a time scale not known to be associated with the star but which is about three times the binary…
Winds in Central Stars of Planetary Nebulae
Modigliani, A.; Patriarchi, P.; Perinotto, M.
We studied five central stars of planetary nebulae with IUE high-resolution spectra to determine the wind properties of their central stars. Using the best stellar and nebular parameters, and analyzing the P Cygni profiles seen in lines of the ions C IV, N V, N IV, O V, O IV, and Si IV with the SEI method, we have obtained the following values of …
Studies of narrow polar rings around E galaxies. II. The UV spectrum of AM 2020-504.
Buson, Lucio; Arnaboldi, Magda; Longo, Giuseppe +2 more
Four ultraviolet (UV) full-shift spectra secured with the IUE satellite have been used to test the accretion scenario for the still unexplored class of the "narrow" polar ring (PR) galaxies. The UV energy distribution in the λλ 1200 - 3300 A range for the "prototype" of this class, the system AM 2020-504, is found to be different from the UV emiss…
The structure of Jupiter's Io plasma torus inferred from Ulysses radio occultation observations
Pätzold, M.; Bird, M. K.; Asmar, S. W. +3 more
The radio downlinks from Ulysses were monitored during the passage of the spacecraft through the Io plasma torus shortly after closest approach to Jupiter. The electron content of the Io torus was derived from the dispersive phase shift of the S-band (2.3 GHz) signal with respect to the X-band (8.4 GHz) signal. Corrections were applied for non-Jov…