Search Publications
Broad, Variable Absorption Lines in the Seyfert Galaxy NGC 3516: Probing the Structure of the Emssion-Line Regions
Voit, G. Mark; Shull, J. Michael; Begelman, Mitchell C.
Nineteen short-wavelength IUE archive images were analyzed in order to probe the structure of the active nucleus in NGC 3516, an SB0 Seyfert I galaxy. The measurements of these features are presented, and the strength, variability, and morphology of the emission and absorption lines and their relation to the continuum are analyzed. It is shown tha…
Multiwavelength monitoring of the dwarf nova VW Hydri. V. EXOSAT observations.
Heise, J.; van der Woerd, H.
Exosat X-ray observations of VW Hyi during three normal outbursts and one superoutburst were obtained in 1984. The decrease in X-ray flux by a factor of 1.2-1.6 during the quiescent periods between outbursts implies that the accretion rate onto the white dwarf decreases by about the same factor, consistent with emission from an optically thin hot …
Detection of Neutral Oxygen and Sulfur Emissions near Io Using IUE
Skinner, T. E.; Feldman, P. D.; Moos, H. W. +6 more
Two very long IUE exposures obtained with precise control of the spacecraft pointing show emissions due to neutral oxygen and sulfur near Io. The emitting region is centered on Io and is less than five Io diameters across. The two spectra obtained near eastern and western elongation in 1986 July and October, respectively, are similar, independent …
The carbon-poor halo planetary nebula DDDM-1.
Clegg, R. E. S.; Torres-Peimbert, S.; Peimbert, M.
The authors have analysed ultraviolet and optical spectra of DDDM-1, a planetary nebula in the galactic halo. Abundances of N, O, S, Ne and Ar are all about a factor 6 lower than solar, while Fe and Mg are deficient by a further factor of 3. No carbon lines were seen in any spectra, and the authors obtain the upper limit C/H < 1.4×10-5
Rotational modulation and flares on RS CVn and BY DRA stars. VI. Physical parameters of the chromospheres/transition regions of V711 Tau (HR 1099), II Peg and AR Lac during october 1981.
Doyle, J. G.; Linsky, J. L.; Rodono, M. +2 more
Ground-based optical and IUE satellite-ultraviolet observations of three RS CVn stars are combined with density sensitive line ratios and differential emission measure curves to describe the physical conditions in their outer atmospheres. Solar-like densities are found to be representative of average conditions on two of the stars, V 711 Tau and A…
General Features of Comet p/ Halley - Solar Wind Interaction from Plasma Measurements
Anderson, K. A.; Reme, H.; Korth, A. +8 more
The Giotto RPA-COPERNIC plasma experiment identified several regions in which the solar wind interaction with the cometary plasma displayed characteristic features: (1) Beginning ∼4.6×106km from the comet there is an upstream region with sporadic connection to the comet, (2) An electron foreshock is present up to 2.5×105km aw…
Ion Temperature and Flow Profiles in Comet p/ Halley's Close Environment
Schwenn, R.; Balsiger, H.; Goldstein, R. +5 more
The HIS instrument of the ion mass spectrometer on board the Giotto spacecraft identified the contact surface at 4800 km distance from the comet nucleus. This boundary is clearly seen by a drastic drop in the temperatures of different ion species from about 2000 K outside to values as low as 300 K inside. Also, inside the contact surface an outflo…
High-energy gamma-ray and hard X-ray observations of CYG X-3.
Strong, A. W.; Hermsen, W.; Pollock, A. M. T. +7 more
High-energy (70 MeV < E < 5 GeV) gamma-ray observations of Cyg X-3 by the ESA satellite COS-B and hard X-ray (14 keV < E < 140 keV) observations by the Leiden-MIT balloon experiment, Leimit, are presented. A comparison with, and a study of earlier results over the 14 decades in energy from 1 keV up to ≡1017eV indicates that …
High-frequency oscillations from CIR X-1.
Tennant, A. F.
The author reports results from an EXOSAT observation of Cir X-1 during which strong, low-frequency (5-20 Hz) quasi-periodic oscillations (QPO) were detected. QPO were also detected at much higher frequencies (100-200 Hz). These high frequencies are consistent with rotation periods in the inner accretion disc region. High-frequency QPO lend weight…
Ultraviolet Observations of Extensive Variability in the Stellar Wind of ξ Persei
Howarth, Ian D.; Prinja, Raman K.; Henrichs, Huib F.
Fifty-six high-resolution ultraviolet IUE observations of ξ Per [O7.5 III] are presented. The optically thick C IV and N V resonance doublets yield a terminal velocity of v = 2600 km s-1. The spectra reveal dramatic variability in the Si IV P Cygni profiles down to short time scales (≡1 hr). The morphology of the variations is character…