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The Giotto electron plasma experiment
Anderson, K. A.; Reme, H.; Korth, A. +11 more
The RPA-Copernic experiment aboard Giotto is described. The experiment is designed to measure the three-dimensional distributions of electrons between 10 eV and 30 keV (by the RPA-1 EESA spectrometer) and the composition and distribution, close to the comet, of thermal positive ions in the mass range 10-213 amu (by the RPA-2 PICCA electrostatic ma…
Study of multiple nucleus galaxies. II. MKN 739.
Kollatschny, W.; Fricke, K. J.; Netzer, Hagai
An investigation of the Markarian galaxy MKn 739 is reported. The investigation used spectroscopic data from ground and space, radio observations, IRAS data and CCD imaging. Component A is a Seyfert type 1 nucleus with strong Fe II lines, very steep continuum and no trace of Lyman alpha and CIV 1549. Component B is a starburst nucleus, quite simil…
Power spectra, with application to EXOSAT data.
Tennant, A. F.
It is shown how an instrumental effect, coupled with the on-board computer sampling, affects the pulse-height analysis data obtained from Exosat, and analytic expressions are developed to remove these effects from the data for the case of small source variability. In the method, the expectation of the power spectrum is the Fourier transform of the…
Further Observations of the Peculiar Hot Helium-rich Degenerate KPD 0005+5106
Sion, Edward M.; Holberg, J. B.; Liebert, James +1 more
A variety of new ultraviolet and optical spectroscopic observations of the peculiar, hot, helium-rich degenerate KPD 0005+5106 are presented. While the expected lines of helium appear, the only detected transitions from a heavier element assignable to the stellar photosphere is the N V 1240 Å doublet, from which an atmospheric abundance is derived…
The central X-ray source in M 33.
Pietsch, W.; Hasinger, G.; Gottwald, M.
The Local Group galaxy M33 was observed with the European X-ray observatory Exosat. Two of the previously reported 11 X-ray sources in M33 were detected; analysis confirmed the dominance of the source M33 X-8, which coincides with the nucleus of M33. With an 0.1-6 keV X-ray luminosity of about 1.5 x 10 to the 39th erg/s, it is the brightest steady…
Secondary Electron Emission Induced by Gas and Dust Impacts on Giotto VEGA-1 and VEGA-2 in the Environment of Comet p/ Halley
McDonnell, J. A. M.; Grard, R. J. L.; Grun, E. +1 more
Giotto, Vega-1 and Vega-2 have been bombarded by a flow of gas and dust particles during their flyby of comet Halley. The emission of secondary electrons and sputtered ions caused by the large impact velocities (70-80 km s-1) perturbed the plasma density in the spacecraft vicinity and was a possible source of interference for electric f…
X-ray spectrum of sigma Geminorum : an RS Canum Venaticorum type binary.
Singh, K. P.; Westergaard, N. J.; Schnopper, H. W. +4 more
The binary system Sigma Gem has been observed on three occasions during 1984 November 17-21 with the medium-energy and the low-energy detectors on the Exosat Observatory. Spectral analysis of the data obtained over the energy range of 0.05-6.0 keV shows evidence for a bimodal temperature distribution of emission measure in an optically thin therma…
Periodic Variabilities in the IUE Spectra of Ss-Cygni
Gaudenzi, S.; Giovannelli, F.; Lombardi, R.
The analysis of the IUE low resolution spectra of SS Cyg in quiescence clearly shows modulations with the orbital phase of the continuum and the emission lines total area. The shape of such modulations is depending on the type of the optical outburst preceding the quiescent phase in which the UV spectra were collected. This behaviour, together wit…
Ultraviolet detection of the nucleus of NGC2440
Heap, S. R.
In a recent letter, Atherton et al.1 announced the detection of the central, exciting star of the planetary nebula, NGC2440, on a narrow-band charge-coupled device (CCD) image obtained under excellent seeing conditions (1 arc s). They found it to be one of the hottest stars known. Here, we report the detection of the same star in ultrav…
Pick-up ions at Comet P/Halley's bow shock - Observations with the IIS spectrometer on Giotto
Johnstone, A.; Borg, H.; Amata, E. +2 more
Gaseous material expanding from the nucleus of Comet Halley into space forms the neutral coma around the comet. Ionization in the solar UV radiation removes particles from the coma and injects them into the solar wind plasma. These freshly created ions are accelerated by the interplanetary electric field on cycloidal trajectories with gyrocenters …