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The highly ionised absorbing material in MR2251-178
Mineo, T.; Stewart, G. C.
Ginga observations have suggested the presence of iron absorption edges at energies appropriate for highly ionised material in the X-ray spectra of a significant number of active galactic nuclei. Here, we present a detailed self-consistent analysis of a series of Ginga and EXOSAT observations of MR2251-178, the original prototype of this warm-abso…
ULF waves in the Io torus: Ulysses observations
Forsyth, R. J.; Rezeau, L.; Lin, Naiguo +7 more
Throughout the Io torus, Ulysses has observed intense ULF wave activity in both electric and magnetic components. Such ULF waves have been previously suggested as the source of ion precipitation leading to Jovian aurorae. The peaks of the wave spectra are closely related to the ion cyclotron frequencies, which is evidence of the waves being ion cy…
Boundary layer ion composition at Jupiter during the inbound pass of the Ulysses flyby
Woch, J.; Galvin, A. B.; Mall, U. +3 more
During the inbound segment of the Ulysses flyby of Jupiter, there were multiple incursions into the dawnside low-latitude boundary layer, as identified by Bame et al. ( Science257, 1539-1542, 1992) using plasma electron data. In the present study, ion composition and spectral measurements provide independent collaborative evidence for the existenc…
Correlations between magnetic field and electron density observations during the inbound Ulysses Jupiter flyby
Dougherty, M. K.; Balogh, A.; Kellogg, P. J. +2 more
The spacecraft Ulysses flew through the Jovian magnetosphere during February 1992. This paper compares the magnetic field observations recorded during the inbound pass of the flyby with the electron density as derived from the URAP instrument. In general, it is expected that the density variations will anti-correlate with the magnetic field streng…
Faint Object Spectrograph Spectra of the UV Emission Lines in NGC 5548: Detection of Strong Narrow Components
Crenshaw, D. Michael; Wu, Chi-Chao; Boggess, Albert
Ultraviolet spectra of the Seyfert 1 galaxy NGC 5548 were obtained with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope on 1992 July 5, when the UV continuum and broad emission lines were at their lowest ever observed level. The high resolution of the spectra, relative to previous UV observations, and the low state of NGC 5548 al…
A 4.86-h periodic modulation in the UV resonance lines of the cataclysmic variable V795 Herculis.
Prinja, Raman K.; Rosen, Simon R.
Low-resolution IUE spectroscopy of V795 Her secured in 1992 August is used to authenticate the presence of an approximately 4.86-h periodic variation in the mainly wind-formed Si IV 1400-A and C IV 1549-A resonance lines. The modulation is demonstrated to be coherent across a 3-yr time-span, and is discordant with the mooted orbital (optical spect…
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…