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Discrete wave packets at the proton cyclotron frequency at comet P/Halley
Neubauer, F. M.; Mazelle, C.
We present in this letter the first experimental evidence for wave packets near the local proton cyclotron frequency in the plasma environment of a comet. The observations have been made by the GIOTTO magnetometer experiment (MAG) around comet P/Halley on both sides of closest approach. The waves are always left-handed in the spacecraft frame, ell…
On the nature of the blue light in central cluster galaxies.
Fabian, A. C.; Crawford, C. S.
An excess blue component of light, extended over the innermost few kpc, is observed in several central cluster galaxies. Using a combination of blue optical spectra and IUE data, we show that the spectrum of the excess blue light is consistent with both star formation dominated by the light of B5 stars, and power-law spectra with slopes between λ^…
Saturn's Upper Atmospheric Hazes Observed by the Hubble Space Telescope
Karkoschka, Erich; Tomasko, Martin G.
We observed Saturn with the Hubble Space Telescope at wavelengths 0.30-0.89 µm for the purpose of determining the distribution of hazes. In the stratosphere, haze optical depths in the ultraviolet are essentially zero for midnorthern latitudes, are small (∼0.2) at low latitudes and mid-southern latitudes, but large (almost unity) above 70° n…
Correlated variations of UV and radio emissions during an outstanding Jovian auroral event
Moos, H. W.; Bame, S. J.; Zarka, P. +6 more
An exceptional Jovian aurora was detected in the FUV on December 21, 1990, by means of Vilspa and Goddard Space Flight Center (GFSC) International Ultraviolet Explorer (IUE) observations. This event included intensification by a factor of three between December 20 and 21, leading to the brightest aurora identified in the IUE data analyzed, and, in…
PG 0308+096 and PG 1026+002: Two New Short Period Binary Stars Resulting From Common-Envelope Evolution
Green, Richard F.; Sion, Edward M.; Saffer, Rex A. +5 more
Ultraviolet spectroscopy, optical spectroscopy, and spectrophotometry have been used to study the excess UV stars PG 0308 + 096 and PG 1026 + 002. Both objects are short-period binary systems, each containing a DA white dwarf star and a dM star. Orbital periods of approximately 0.284 day for PG 0308 + 096, and aproximately 0.597 day for PG 1026, h…
Spectral analysis of DY Centauri, a hot R Coronae Borealis star with an unusually high hydrogen content.
Heber, U.; Jeffery, C. S.
The photospheric parameters of DY Cen, an H-deficient early-B supergiant that is spectroscopically similar to the pulsating, extreme-He star BD-9 deg 4395, have been derived from high-resolution spectra via atomic data and line-blanketed model atmospheres. DY Cen is shown to be a metal-poor EHe star whose composition supports an anticorrelation be…
A Cluster of Nascent Galaxies at Z = 2?
Dressler, Alan; Oemler, Augustus, Jr.; Gunn, James E. +1 more
On a 6 hr Wide Field Camera exposure with the Hubble Space Telescope of the rich cluster CL 0939+4713, we have identified an apparent cluster of ~30 faint, extended objects with magnitudes 22 < r < 25. The objects are typically 1" in size with bright central regions only a few tenths of an arcsecond in size, and are distributed over a region…
Excitation Rate Coefficients and Line Ratios for the Optical and Ultraviolet Transitions in S II
Cai, Wei; Pradhan, Anil K.
New calculations are reported for electron excitation collision strengths, rate coefficients, transition probabilities, and line ratios for the astrophysically important optical and UV lines in S II. The collision strengths are calculated in the close coupling approximation using the R-matrix method. The present calculations are more extensive tha…
UV spectral variability in the Herbig AE star HR 5999. 11: The accretion interpretation
Grady, C. A.; Perez, M. R.; The, P. S.
We report recent IUE high- and low-dispersion observations with the IUE long wavelength camera (LWP) and short wavelength camera (SWP) of the Herbig Ae star HR 5999. We have found a dramatic change in the structure of the Mg II h and k lines (2795.5, 2802.7 Å) along with some continuum flux excesses especially at the short end of the SWP camera. L…
Low-frequency electromagnetic plasma waves at comet P/Grigg-Skjellerup analysis and interpretation
Coates, A. J.; Neubauer, Fritz M.; Glassmeier, Karl-Heinz +1 more
The propagation and polarization characteristics of low-frequency electromagnetic wave fields near comet P/Grigg-Skjellerup (P/GS) are analyzed using magnetic field and plasma observations obtained by the Giotto magnetometer experiment and the Johnstone plasma analyzer during the encounter at the comet on July 10, 1992. The results have been physi…