Search Publications
The ULYSSES energetic particle composition experiment EPAC
Woch, J.; Keppler, E.; Korth, A. +4 more
The purpose of this paper is to briefly describe the EPAC investigation aboard the Ulysses spacecraft. The EPAC sensor will measure the fluxes, angular distributions, energy spectra, and composition of ions in the energy range from 300 keV/nucleon to 25 MeV/nucleon. Some measurements will be shown obtained after turn-on in interplanetary space.
Titan: Evidence for seasonal change—A comparison of Hubble space telescope and voyager images
Weaver, H. A.; Tomasko, M. G.; Caldwell, John +7 more
Images of Titan were obtained by the Hubble Space Telescope (HST) on 26 August 1990. Comparison with Voyager 1 and Voyager 2 images obtained 10 and 9 years earlier shows that the seasonal hemispheric brightness asymmetry has reversed near 440 and 550 nm wavelengths, with the northern hemisphere now being brighter. An additional, noisy HST image at…
A Survey of Ultraviolet Variability in Blazars
Edelson, Rick
This is the first comprehensive consistent survey of the ultraviolet variability properties of a large sample of blazars. All of the 14 blazars with five or more observations in a single IUE, camera showed significant variability. The strength of the ultraviolet variability is positively correlated with both the apparent ultraviolet luminosity and…
PU Vulpeculae : the outburst of a symbiotic nova.
Vogel, M.; Nussbaumer, H.
We report the full history of PU Vulpeculae from outburst to 1991 as seen in its ultraviolet emission. We show that PU Vul is a symbiotic nova, which went into outburst in 1977 after a nova-like thermonuclear event. The outbursting object went first into an F supergiant phase. The spectrum evolved between 1979 and 1989 from F-type into that of Ao.…
In-orbit performance of the HIPPARCOS astrometry satellite
Grewing, M.; Lindegren, L.; Turon, C. +7 more
Launched in August 1989 into a geostationary transfer orbit, the Hipparcos astrometry satellite failed to reach its intended geostationary orbit through the failure of its apogee boost motor. Present indications are that the possible operational lifetime should nevertheless extend beyond the end of 1992, with extremely high-quality scientific data…
An Interpretation of the Spectral Properties of Hot Hydrogen-rich White Dwarfs with Stratified H/He Model Atmospheres
Vennes, Stephane; Fontaine, Gilles
A grid of stratified H/He model atmospheres applicable to the interpretation of the spectral properties of hot H-rich white dwarfs (WDs) is computed. Samples of hot DA WDs observed with Exosat and Einstein are analyzed using the models. Six out of six objects with T(eff) = 35,000 K or less do not show a EUV/soft X-ray flux deficiency and therefore…
The onset and growth of the 1990 equatorial disturbance on Saturn
Beebe, R. F.; Barnet, C.; Murrell, A. S. +1 more
The development of cloud structures at low Saturnian latitudes in September 1990 can be divided into three phases: the onset and expansion of the initial disturbance (popularly known as the Great White Spot), the eastward and westward expansion of the bright cloud, and the eventual formation of wave-like structures encircling the equator. The thre…
Rapid Oscillations in Cataclysmic Variables. VIII. YY Draconis (=3A 1148+719
Caillault, J. -P.; Schwartz, D. A.; Williams, G. A. +3 more
A 16th magnitude cataclysmic variable presumably a dwarf nova, was detected near one of the positions permitted for the hard (2-10 keV) X-ray source 3A 1148 + 719. The optical and UV spectra of YY Dra are fairly typical of cataclysmic variables, except that the TiO absorption bands of an M dwarf can be seen for greater than 5000 A. This shows that…
Ulysses Dust Measurements Near Jupiter
Morfill, Gregor E.; Kissel, Jochen; Schwehm, Gerhard +13 more
Submicrometer- to micrometer-sized particles were recorded by the Ulysses dust detector within 40 days of the Jupiter flyby. Nine impacts were recorded within 50 Jupiter radii with most of them recorded after closest approach. Three of these impacts are consistent with particles on prograde orbits around Jupiter and the rest are believed to have r…
Faint object camera observations of M 87 : the jet and nucleus.
Boksenberg, A.; Barbieri, C.; Weigelt, G. +16 more
Ultraviolet and optical images of the central region and jet of the nearby elliptical galaxy M87 have been obtained with ~0.1 arcsec resolution in several spectral bands with the Faint Object Camera (FOC) on the Hubble Space Telescope, including polarisation images. Deconvolution enhances the contrast of the complex structure and filamentary patte…