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Magnetic structure in cool stars. XII - Chromospheric activity and rotation of giants and dwarfs
Rutten, R. G. M.
The relation between the Ca II H and K line-core flux density and rotation rate is studied for 313 F- to M-type stars ranging in luminosity class from II-III to V. The activity-rotation relation for Ca II is compared with similar relations for Mg II and soft X-rays. Dwarfs and the majority of the giants studied follow the same color-dependent rela…
Rotational modulation and flares on RS CVn and BY DRA stars. III. IUEobserations of V711 Tau = (HR 1099), II Peg and AR Lac.
Doyle, J. G.; Linsky, J. L.; Simon, T. +8 more
The authors present observations of three RS CVn stars, which were obtained over the stellar rotation cycles with the IUE satellite. Emission lines from high-temperature transition regions and chromospheres analogous to those observed in the solar spectrum were observed. However, the stellar line surface fluxes are hundreds of times the solar valu…
IUE Observations of Comet p/ Halley - Evolution of the Ultraviolet Spectrum Between 1985SEP and 1986JUL
Feldman, P. D.; A'Hearn, M. F.; Schleicher, D. G. +13 more
The ultraviolet spectrum of comet P/Halley (1982 i) was monitored with the International Ultraviolet Explorer (IUE) satellite observatory between 1985 September 12 and 1986 July 8 (r < 2.6 AU pre- and post-perihelion) at regular time intervals except for a two-month period around the time of perihelion. A complete characterization of the UV spe…
The beta Pictoris circumstellar disk. IV. Redshifted UV lines.
Ferlet, R.; Vidal-Madjar, A.; Lagrange, A. M.
Several new and archive observations with the International Ultraviolet Explorer have confirmed the variability of the UV circumstellar absorption lines of Fe II and Mg II toward β Pic. The authors furthermore show that all these variations take place on the red wing of the lines, in material which is moving toward the star. Tentative scenarios ar…
The radio to X-ray continuum emission of the quasar 3C 273 and its temporal variations.
Bouchet, P.; Falomo, R.; Gear, W. K. +7 more
Quasi-simultaneous multifrequency observations from radio to X-rays of the bright quasar 3C273 for several epochs between December 1983 and March 1986 are presented. The light curves in the different wavebands and the overall spectral energy distribution are analyzed. The NIR and optical fluxes showed small variations during the period considered,…
Rotational modulation and flares on RS CVn and BY DRA stars. VI. Physical parameters of the chromospheres/transition regions of V711 Tau (HR 1099), II Peg and AR Lac during october 1981.
Doyle, J. G.; Linsky, J. L.; Rodono, M. +2 more
Ground-based optical and IUE satellite-ultraviolet observations of three RS CVn stars are combined with density sensitive line ratios and differential emission measure curves to describe the physical conditions in their outer atmospheres. Solar-like densities are found to be representative of average conditions on two of the stars, V 711 Tau and A…
Star formation in nuclei of SO/E galaxies.
Rocca-Volmerange, B.; Guiderdoni, B.
Spectra of nuclei for some lenticular and elliptical galaxies observed from the IUE satellite in the far-UV light are analyzed with the help of the IUE spectral atlases using an almost similar resolution for galaxies and stars, down to about 8A for a significant signal/noise ratio. In the 2500A-3150A wavelength range, all gas-poor galaxies show 'r…
Magnetic structure in cool stars. XIII - Appropriate units for the rotation-activity relation
Rutten, R. G. M.; Schrijver, C. J.
The paper compares relations between coronal and chromospheric emissions, and between activity and stellar rotation, in which the radiative emissions that measure the magnetic activity of cool stars are expressed in different units. The surface flux density appears to be the most suitable unit in which to express the radiative emission measuring s…
Photometric properties of SN 1987A and other sources in the same field.
Panagia, N.; Clavel, J.; Wamsteker, W. +5 more
The authors find that the UV flux of SN 1987A declines since the very first IUE observation at a rate which is faster at shorter wavelengths while the emission around 5100 Å increases slowly but steadily with time. Thus, the UV radiation dominates the overall emission at early phases but becomes completely negligible at later phases. Such an evolu…
EUV photometry of DA white dwarfs with EXOSAT.
Jordan, S.; Koester, D.; Brunner, H. +1 more
The authors present EXOSAT EUV observations for 9 white dwarfs of spectral type DA. These are analysed together with other observational data from the literature using theoretical model atmospheres. For 8 objects He/H abundance ratios and interstellar hydrogen column densities are obtained. The data for HZ 43 seem to contradict recent results of o…