Search Publications
Missions
Journals
Publication Years
Evidence for Langmuir wave collapse in the interplanetary plasma
Goetz, K.; Kellogg, Paul J.; Monson, S. J. +1 more
With the Fast Envelope Sampler part of the URAP experiment on Ulysses, we have observed much rapidly varying structure in plasma waves in the solar wind. Here we discuss extremely narrow (1 ms) structures observed together with electrostatic Langmuir waves, as well as some broader Langmuir wave packets
Hubble space telescope observations of the 1990 equatorial disturbance on Saturn: Zonal winds and central Meridian albedos
Beebe, R. F.; Westphal, J. A.; Barnet, C. D. +1 more
Two sets of Hubble Space Telescope (HST) data, obtained in August 1990 and November 1990, are compared with Voyager 1 and 2 data acquired in 1980 and 1981. A rare disturbance developed in the equatorial region of Saturn in late September 1990. Due to the large equatorial wind shear, this disturbance generated inhomogeneous bright cloud structures …
The Ultraviolet Absorption Spectrum of the Quasar H1821+643 (z = 0.297)
Schneider, Donald P.; Green, Richard F.; Jannuzi, Buell T. +2 more
We report measurements of the absorption lines in the ultraviolet spectrum of the nearby luminous quasar H1821+643 (z = 0.297). The results were obtained using high-resolution observations with the faint object spectrograph of the Hubble Space Telescope. A total of 51 absorption lines and a number of emission features were detected between 1190 an…
The Constitution of the Atmospheric Layers and the Extreme Ultraviolet Spectrum of Hot Hydrogen-rich White Dwarfs
Vennes, Stephane
An analysis is presented of the atmospheric properties of hot, H-rich, DA white dwarfs that is based on optical, UV, and X-ray observations aimed at predicting detailed spectral properties of these stars in the range 80-800 A. The divergences between observations from a sample of 15 hot DA white dwarfs emitting in the EUV/soft X-ray range and pure…
Nearly simultaneous observations of chromospheric and coronal radiative losses of cool stars.
Schrijver, C. J.; Dobson, A. K.; Radick, R. R.
The flux-flux relationships of cool stars are studied on the basis of nearly simultaneous measurements of Ca II H+K, Mg II h+k, and soft X-ray fluxes. A linear relationship is derived between IUE Mg II h+k fluxes and Mount Wilson Ca II H+K fluxes which were obtained within 36 hr of each other for a sample of 26 F5-K3 main-sequence stars. Nearly si…
The Hubble Space Telescope Observations of X-Ray Nova MUSCAE 1991 and Its Spectral Evolution
Panagia, N.; Horne, Keith; Shrader, C. R. +4 more
Hubble Space Telescope Faint Object Spectrograph (FOS) Faint Object Camera (FOC) and observations of Nova Muscae 1991 obtained on May 14-15, 1991 are presented and discussed. A nearly featureless continuum with broad 2200 A absorption feature and no Balmer jump is found. The FOS spectrum is modeled, including previous multiepoch IUE, optical, and …
Time Series Observations of O Stars. I. IUE Observations of Variability in the Stellar Wind of zeta Puppis
Howarth, I. D.; Bolton, C. T.; Prinja, R. K. +7 more
Stellar wind variability in Zeta Pup (O4 I(n)f) is described based on 31 high-resolution IUE observations secured over 5 1/2 days in 1989 April. Extensive changes are evident in the absorption regions of Si IV 1393.76, 1402.77A and N IV 1718.55A P Cygni profiles. Both lines exhibit similar patterns of variability, which are characterized by the de…
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…