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Phase variations of 88 Herculis : do the UV observations confirm a connection between these variations and the changes of the phospheric parameters of the underlying star ?
Zorec, J.; Hoeflich, P.; Divan, L.
It is shown that the observed far-UV flux variation of 88 Herculis from 1976 to 1979 is lower than previously reported. The variation from 1979 to 1983 is difficult to confirm. The remaining flux changes cannot be attributed to changes in the stellar luminosity of the star. Furthermore, the constancies of the size and of the position-wavelength of…
MG II Line Profiles of the Mira S Carinae
Brown, Alexander; Bookbinder, Jay A.; Brugel, Edward W.
A series of high-dispersion IUE observations obtained to investigate the evolution of the shock structure of the Mira variable S Carinae have produced (despite limited phase coverage) a set of five exceptionally interesting spectra of the Mg II h and k lines. The two primary findings of these observations are (1) there is significant emission from…
Evidence for near-surface breezes on Comet P/Halley
Keller, H. U.; Thomas, N.
Halley Multicolor Camera (HMC) images taken of the nucleus of Comet P/Halley and its environment from on board ESA's spacecraft, Giotto, provide substantial evidence for flow of dust particles almost parallel to the surface at small cometocentric distances. This evidence is summarized and discussed with reference to other spacecraft experiments, g…
In situ exploration of the dusty coma of comet P/Halley at Giotto's encounter: Flux rates and time profiles from 10-19kg To 10-5kg
Green, S. F.; Kissel, J.; McDonnell, J. A. M. +4 more
Flux rates and time profiles from the Giotto DIDSY and PIA experiments are presented in the light of more refined data analysis and increased data coverage. The methods of data analysis for both experiments are explained, together with the relevant behaviour of their in-flight performance. A mass distribution from 237 000km to 11 500km from comet …
X-ray spectrum of the BL Lacertae object PKS 2155-304.
Koyama, K.; Warwick, R. S.; Makishima, K. +4 more
The BL Lacertae object PKS 2155-304 was observed with Ginga for two days in May 1987. The 2-35 keV intensity showed a significant variability, the most rapid change being a 30 percent increase in 3 hr. The X-ray spectrum was described by a single power-law model with photon spectral index ranging between 2.7 and 2.9, but the power-law slope showed…
Mechanisms of dust emission from the surface of a cometary nucleus
Spohn, T.; Thiel, K.; Krankowsky, D. +9 more
Cometary nuclei consist of mixtures of ices and non-volatile particulates in mass proportions of similar magnitudes. Dust is carried by the gas drag of the sublimating ices. Gas drag from free expansion of the gases from the nucleus dominates the acceleration of dust particles after their release from the surface. Significant gas pressure can buil…
Stellar wind velocities and luminosities of O stars.
Stalio, R.; Bernabeu, G.; Magazzu, A.
Stellar wind velocities (v-edge not greater than v-infinity) for 110 O stars are calculated. The spectral types in the sample range from O3 through B0; all luminosity classes are represented. Stars from clusters and associations (extreme Population I) as well as field stars are considered. There is a weak evidence of higher v-edge for extreme Popu…
Far-Ultraviolet Spectrophotometry of SPICA
Snow, Theodore P.; Cook, Timothy A.; Cash, Webster
A spectrum of the star Spica (Alpha Virginis) from 960 to 1270 A was recorded by a rocket-borne spectrograph March 13, 1988. The spectrum, which has 3.4 A resolution, shows a much sharper drop-off in intensity near 1050 A than similar measurements made by the Voyager UVS, but is in good agreement with the spectrum obtained by Brune et al. in a 197…
The Binary Companion of the Classical Cepheid AW Per
Evans, Nancy Remage
An analysis of IUE spectra of the companion of AW Per shows it to be an extreme BpSi/HeW star with a spectral type of B7 V to B8 V. The flux of the composite spectrum from 1200 A through V is found to be well matched by F7 Ib and B8 V standard stars with Delta M(V) = 3.1 mag. The results suggest that the mass of the Cepheid must be greater than 4.…
Rotational modulation and flares on RS Canum Venaticorum and BY Draconis stars. XII. Near-to-simultaneous high resolution UV and optical observations of II Pegasi during July 1984.
Doyle, J. G.; Byrne, P. B.; Marang, F. +4 more
Nearly simultaneous high resolution ground-based optical and IUE satellite UV spectroscopy and an optical light curve of the RS CVn star II Peg are presented. It is shown that the chromospheric and transition region radiative losses of the star in July 1984 are lower than previously recorded means. The flux in the Lyman-alpha line is estimated and…