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Elemental abundances in normal late-B and HgMn stars from co-added IUE spectra. I. Iron-peak elements.
Dworetsky, M. M.; Smith, K. C.
The abundances of five iron-peak elements (chromium through nickel) in a sample of forty normal, superficially normal, and HgMn-type late-B stars are derived by spectrum-synthesis analysis of co-added high-resolution International Ultraviolet Explorer (IUE) spectra. Approximately solar abundances of these elements are obtained for the normal stars…
The extended formaldehyde source in comet P/Halley
Eberhardt, P.; Meier, R.; Krankowsky, D. +1 more
The Neutral Mass Spectrometer on the Giotto spacecraft measured the neutral and ion composition in the coma of comet P/Halley. In the ion mass spectra, the 31 amu/e peak is dominated by the protonated formaldehyde ion H3CO+ and can be used to calculate the H2CO density. The radial profile of the amplitude of the 31…
A model for the 89 Herculis system.
Waters, L. B. F. M.; Mayor, M.; Trams, N. R. +1 more
We report new radial velocity measurements of the F2 supergiant 89 Her that confirm the binary nature of this star. A period search yields an orbital period of 288.4 +/- 0.7 days, in close agreement with earlier results. We also present intermediate resolution spectra in the wavelength range 3500 - 11,000 A, with numerous emission lines. We use th…
On the relative C,N,O abundances and the evolutionary status of yellow symbiotic stars.
Nussbaumer, H.; Schmid, H. M.
Symbiotic binaries consist of a cool giant and a hot radiation source, which is ionizing the nebula associated with the system. Yellow symbiotic stars can be divided according to their IR colors into s-type (stellar) and d'-type (dust) systems. The s-types are relatively narrow systems, with orbital periods of several hundred days. They contain hi…
First results from the Giotto magnetometer experiment during the P/Grigg-Skjellerup encounter
Glassmeier, K. -H.; Neubauer, F. M.; Pohl, M. +9 more
The Giotto magnetic field experiment has provided the first magnetic field data on the interaction between the solar wind and a low gas production comet, P/Grigg-Skjellerup. Waves produced by ion pick-up instabilities have been observed throughout the interaction region with particularly simple waveforms at large distances and a rich phenomenology…
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 …
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…
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…
SAO 244567 : a post-AGB star which has turned into a planetarey nebula within the last 40 years.
Pottasch, S. R.; Clavel, J.; de Martino, D. +5 more
SAO 244567 (Hen 1357 = CPD -59 deg 6926 = IRAS 17119-5926) is an IRAS source with far infrared colors and flux distribution similar to those of planetary nebulae. The IUE ultraviolet spectra obtained in July 1988 and April 1992 show nebular emission lines, and also the changes in the spectra suggest the formation of the planetary nebula and the ra…