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Observations of the Solar Wind and Cometary Ions during the Encounter Between Giotto and Comet Grigg-Skjellerup
Coates, A. J.; Winningham, J. D.; Borg, H. +6 more
The solar wind interaction with the outfiowing gas from a second comet has been recorded by the same in-situ instrumentation that was used for the comet Halley encounter m 1986. The new comet, Grigg-Skjellerup, is the smallest so far observed since the size of the interaction region is comparable with a cometary ion gyroradius Preliminary results …
A survey of low frequency waves at Jupiter: The Ulysses encounter
Tsurutani, Bruce T.; Smith, Edward J.; Balogh, Andre +1 more
We report the results of a survey of low-frequency (LF) plasma waves detected during the Ulysses Jupiter flyby. In the Jovian foreshock, two predominant wave periods are detected: 102-s and 5-s, as measured in the spacecraft frame. The 102-s waves are highly nonlinear propagate at large angles to B\searrow0 (typica…
The EXOSAT Medium Energy (ME) Sample of Dwarf Novae
Mukai, K.; Shiokawa, K.
We present our analysis of the EXOSAT medium energy (ME) archival data on dwarf novae. Many dwarf novae were observed with EXOSAT; unfortunately, a significant fraction resulted in nondetection or marginal detection with the ME instrument. Our analysis of the brightest dwarf nova, SS Cyg, shows little correlation between the count rate and the har…
Optical/UV counterpart of the supersoft transient X-ray source RX J0513.9-6951 in the Large Magellanic Cloud.
Motch, C.; Bianchi, L.; Pakull, M. W. +5 more
Optical and IUE observations of the ROSAT X-ray transient RX J0513.9-6951 show this object to be remarkably similar to Cal 83, the prototype of luminous supersoft sources which is also located in the LMC. The counterpart is a B ~ 17 mag blue star which apparently did not vary much around the time of the X-ray outburst. Spectrophotometry reveals na…
The ion population between 1300 KM and 230000 KM in the coma of comet P/Halley
Altwegg, K.; Balsiger, H.; Geiss, J. +6 more
During the encounter of the spacecraft Giotto with Comet Halley the two sensors of the ion mass spectrometer (IMS), high energy range spectrometer (HERS) and high intensity spectrometer (HIS), measured the mass and the three-dimensional velocity distributions of cometary ions. HIS looked mainly at the cold, slow part of the distribution close to t…
A Hubble Space Telescope Planetary Camera View of Giant H II Regions: The Wolf-Rayet Content of NGC 595 and NGC 604 in M33
Drissen, Laurent; Moffat, Anthony F. J.; Shara, Michael M.
We present images of NGC 595 and NGC 604, the most massive giant H II regions in M33, obtained with the Planetary Camera aboard the Hubble Space Telescope in order to study their Wolf-Rayet (WR) population. Fourteen WR and/or Of candidates are detected in NGC 604, and eleven in NGC 595. All previously claimed "superluminous" WR stars are found to …
Does a Luminosity-dependent Continuum Shape Cause the Baldwin Effect?
Zheng, Wei; Malkan, Matthew A.
We combine ground- and space-based spectrophotometry to measure the luminosity dependence of the shape of the optical/UV continuum in 108 QSO and 37 Seyfert 1 nuclei. The UV continuum at 1250 Å in high-luminosity QSOs, compared with the optical continuum at 6500 Å, is over one magnitude higher than that in the less luminous Seyfert galaxies. In te…
Silicon and Carbon Abundances in the Orion Nebula
Dufour, Reginald J.; Rubin, Robert H.; Walter, Donald K.
We assess the gas-phase abundances of Si and C from our recent measurements of Si(2+), C(2+), and C(+) in the Orion Nebula by expanding on our earlier 'blister' models. The C and Si abundances are derived from new IUE high-dispersion spectra of the C(2+) 1907, 1909 A and Si(2+) 1883, 1892 A lines and archival IUE data. Gas-phase Si/C = 0.016 in th…
Doppler tracking of spacecraft with multi-frequency links
Comoretto, G.; Iess, L.; Bertotti, B.
We discuss the use of multi-frequency microwave links in Doppler tracking of interplanetary spacecraft for scientific purposes, especially in relation to the measurement and the elimination of the contribution due to the plasma in the solar wind and the ionosphere. We show how the two contributions in the up- and the down-link can be separately me…
Ejection of dust from Jupiter's gossamer ring
Hamilton, Douglas P.; Burns, Joseph A.
ONE of the most intriguing discoveries of the Ulysses mission so far has been the detection of periodic, collimated streams of high-velocity, submicrometre-sized dust particles emanating from Jupiter1,2. To explain the Ulysses data, Horanyi et al. showed3 that electromagnetic forces within Jupiter's magnetosphere can accelera…