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The Composition and Dynamics of Cometary Ions in the Outer Coma of Comet p/ Halley
Schwenn, R.; Altwegg, K.; Balsiger, H. +15 more
During its flyby at comet Halley, the Giotto spacecraft encountered high densities of cometary ions inside approximately 200000 km from the nucleus. Their properties changed drastically as the comet was approached. We present here density profiles of solar wind alpha particles and of the major cometary ions as obtained by the IMS-HERS sensor betwe…
X-ray emission from the symbiotic system CH Cygni.
Leahy, D. A.; Taylor, A. R.
CH Cyg was observed with the EXOSAT LE1 telescope and CMA detector with 3 filters on 1985 May 24. The count rates indicate a soft X-ray spectrum with kT ≈ 0.1 keV and column density ≈4×1020 cm-2. The observed flux is ≈1.3×10-11erg cm-2s-1. An earlier upper limit obtained with the Einstein Imag…
Spectral evolution of SN 1987A in the far-ultraviolet.
Panagia, N.; Talavera, A.; Fransson, C. +4 more
Preliminary results are presented on the UV spectral evolution of SN 1987 A from IUE data obtained from February 25 to March 23, 1987. It is suggested that line blanketing, mainly from Fe II, Ni II and Ti II, variable with time, is probably responsible for the observed features. Black body fitting to the UV-optical-infrared energy distribution on …
Interstellar lines in SN 1987A observed with the IUE.
Panagia, N.; de Boer, K. S.; Grewing, M. +3 more
The SN 1987A UV-interstellar spectrum shows nine resolvable components in ionization stages ranging from neutral gas (Mg I, Si II, Fe II, etc.) to highly ionized gas (Al III, Si IV, C IV). Three components are due to gas in the Milky Way disk and halo, four are most likely due to LMC gas, two components are at velocities intermediate to those of t…
Activity of comet P/Halley 23-25 March, 1986 - IUE observations
Feldman, P. D.; A'Hearn, M. F.; McFadden, L. A. +3 more
A large but gradual increase in the brightness of the emission bands of comet Halley and, thus, in the coma abundance of OH, CS, CO2(+), and dust was observed with the International Ultraviolet Explorer (IUE) satellite from Mar. 23 to 25, 1986. This brightness change was also monitored by the Fine Error Sensor (FES) tracking and acquisition camera…
A study of the massive O-type binary IOTA Orionis.
Howarth, I. D.; Stickland, D. J.; Lloyd, C. +1 more
Iota Orionis is an O9 III+B1 III binary with a highly eccentric orbit. Using coudé spectra the authors have updated its ephemeris and established a value for the apsidal motion. Combining the orbital elements, the astrophysical data (the primary is an O9 III standard star in the Orion Association), and photometry through a grazing eclipse, they ha…
Charge Exchange of Solar Wind Ions in the Coma of Comet p/ Halley
Balsiger, H.; Geiss, J.; Goldstein, B. E. +7 more
In addition to solar wind pick-up of cometary ions, charge exchange between solar wind ions and cometary neutrals is, potentially, an important comet-solar wind interaction closer to the nucleus. One monitor of the charge exchange rate is the relative abundances of solar wind He2+ and He+. Radial profiles of these two ions me…
Silicon absorption in UV spectra of AP SI stars.
Lanz, T.; Artru, M. -C.
The authors investigate the role of silicon UV absorption occurring in the atmosphere of early-type stars. A detailed analysis of the λλ1250 - 1850 Å range is presented. High-resolution spectra are obtained from the IUE database for typical silicon stars and for a few normal main-sequence stars. The strongest absorption in these spectra are the re…
An Interpretation of the Ion Pile-Up Region Outside the Ionospheric Contact Surface
Schwenn, R.; Balsiger, H.; Ip, W. H. +3 more
An analysis interrelating some of the results of plasma measurements by the Giotto spacecraft in the inner coma of comet P/Halley suggests that the formation of the plasma pile-up region at a distance of 10,000 km - 30,000 km may be the result of accumulation of ion density in a stagnant flow region with a sharp electron temperature transition for…
The peculiar early-type emission line supergiant S18/SMC : an opticaland ultraviolet study.
Shore, S. N.; Allen, D. A.; Sanduleak, N.
The authors have observed the extreme early-type emission line star S18/SMC during 1978 to 1983 with both optical and ultraviolet low and moderate dispersion spectra. The star is a pronounced variable in He II, C IV, N IV, N V and Si IV. There appear to be no associated photometric variations from λλ1200 to 10,000 Å. A model is presented for the e…