Search Publications
The Interstellar Deuterium-to-Hydrogen Ratio: A Reevaluation of Lyman Absorption-Line Measurements
McCullough, Peter R.
The D/H ratio in the local interstellar medium is evaluated based upon previously published measurements of Lyman absorption lines together with the hypothesis that the D/H ratio is constant. A unique value for the D/H ratio of 1.5 (+/- 0.2) x 10 exp -5 by number is shown to be consistent with all published determinations made with the Copernicus …
Plasma Composition in Jupiter's Magnetosphere: Initial Results from the Solar Wind Ion Composition Spectrometer
Livi, S.; Balsiger, H.; Geiss, J. +10 more
The ion composition in the Jovian environment was investigated with the Solar Wind Ion Composition Spectrometer on board Ulysses. A hot tenuous plasma was observed throughout the outer and middle magnetosphere. In some regions two thermally different components were identified. Oxygen and sulfur ions with several different charge states, from the …
Variability pattern from X-ray to IR wavelengths in the active nucleus ofNGC 1566.
Alloin, D.; Pelat, D.; Baribaud, T. +1 more
This study presents the results of a multiwavelength monitoring of the active galactic nucleus in NGC 1566. Data collected in the X-rays, ultraviolet, visible and near-infrared domains have been combined together, in order to disentangle the various components and to better understand the patterns of variability in this active nucleus. At all wave…
Tomographic Separation of Composite Spectra. I. The Components of Plaskett's Star
Wiggs, Michael S.; Gies, Douglas R.; Bagnuolo, William G., Jr.
The UV photospheric lines of Plaskett's Star (HD 47129), a 14.4 day period, double lined O-type spectroscopic binary were analyzed. Archival data from IUE (17 spectra well distributed in orbital phase) were analyzed with several techniques. A cross correlation analysis, which showed that the secondary produces significant lines in the UV, indicate…
Ulysses at Jupiter: An Overview of the Encounter
Smith, E. J.; Wenzel, K. -P.; Page, D. E.
In February 1992, the Ulysses spacecraft flew through the giant magnetosphere of Jupiter. The primary objective of the encounter was to use the gravity field of Jupiter to redirect the spacecraft to the sun's polar regions, which will now be traversed in 1994 and 1995. However, the Ulysses scientific investigations were well suited to observations…
Preliminary Analysis of an Ultraviolet Hubble Space Telescope Faint Object Camera Image of the Center of M31
Boksenberg, A.; Barbieri, C.; Weigelt, G. +17 more
A 5161 s exposure was taken with the FOC on the central 44" of M31, through a filter centered at 1750 A. Much of the light is redleak from visible wavelengths, but nearly half of it is genuine UV. The image shows the same central peak found earlier by Stratoscope, with a somewhat steeper dropoff outside that peak. More than 100 individual objects …
X-Ray Luminosity and Spectral Variability of Hard X-Ray--selected Active Galactic Nuclei
Tagliaferri, G.; Giommi, P.; Grandi, P. +2 more
One hundred sixty-one observations archived in the EXOSAT data base are analyzed in order to study time and spectral variability of all 30 sion-line active galactic nuclei (AGNs) in the Piccinotti sample. For each source long-term (from days to months) and short-term (from minutes to hours) luminosity variations were sought using the soft (LE: 0.0…
The EXOSAT obseravtions of SS Cygni.
Watson, M. G.; Jones, M. H.
A series of nine observations of SS Cygni made using Exosat between 1983 November and 1984 September are presented. Distinct soft amd hard X-ray emitting components were spectrally resolved by the LE and ME instruments, respectively. In quiescence the source shows hard X-ray emission with a 2-10 keV luminosity of 1.2 x 10 exp 33 (d/200 pc)-squared…
The HIPPARCOS Input Catalogue. I - Star selection
Arenou, F.; Crifo, F.; Gomez, A. +7 more
The Hipparcos Input Catalogue has been compiled, over the period 1982-1991, as the definitive observing catalog for the ESA's Hipparcos satellite, launched on 8 August 1989. It contains the most up-to-date, comprehensive, and homogeneous information on the 118,000 stars being observed by Hipparcos. Its stellar and data content is described in a se…
Hubble Space Telescope Imaging of the North Polar Aurora on Jupiter
Caldwell, J.; Hua, X. -M.; Turgeon, B.
The first direct images of the Jovian aurora at ultraviolet wavelengths were obtained by the Hubble Space Telescope Faint Object Camera near the time of the Ulysses spacecraft encounter with Jupiter on 8 February 1992. The auroral oval is not uniformly luminous. It exhibits a brightness minimum in the vicinity of longitude 180^circ. In the few ima…