Search Publications
Gas motions in and origin of the supergiant shell LMC4.
Bomans, D. J.; de Boer, K. S.; Domgoergen, H.
IUE high-dispersion spectra of stars in the supergiant shell LMC4have been used to derive velocities and column densities of absorbing gas clouds. The HI 21-cm profiles for the LMC4region from the LMC data of Rohlfs et al. (1984) have been analysed and interpreted in cloud components. Combining the absorption and emission line data, a detailed pic…
Non-LTE line formation for iron group elements. III. Fe IV.
Butler, K.; Becker, S. R.
A non-LTE line formation calculation for FeIV is introduced. The data for radiative bound-bound transitions which have been derived as part of this work are described and their accuracy is evaluated. The theoretical non-LTE spectrum of FeIV is compared to the HST spectrum of BD+75 325 and the IUE spectrum of Feige 67 both of which are classified a…
Multiwavelength analysis of active galaxies: implications on unified Seyfert models.
Mas-Hesse, J. M.; Rodriguez-Pascual, P. M.; Wamsteker, W. +4 more
We have analyzed the multiwavelength (radio to X-rays) observational properties of a sample of 111 galaxies covering a wide range of activity (QSO, Seyfert 1 and 2 and star forming galaxies), with the aim of looking for similarities and systematic differences between the different sub-classes, which could provide some clues about the nature of the…
Surface carbon abundances and compositional stratification of cool helium-rich white dwarfs.
Koester, D.; Weidemann, V.
From the ultraviolet lines of CI in IUE spectra of the DQ white dwarfs L 845-70, GD 84, and G 188-27 we determine a surface carbon abundance of logC/He=-7, and T_eff_=9250, 9000 and 11000K. Comparison with the results for other stars of the same spectral class indicates variations in carbon abundance at the same temperature. If the carbon is the r…
The β Pictoris phenomenon among young stars. II. UV observations of the Herbig AE star UX Orionis.
Talavera, A.; Grady, C. A.; Perez, M. R. +4 more
IUE spectra of the Herbig Ae star UX Ori reveal the presence of large amplitude light and color changes, which are an extension to shorter wavelengths of the "blueing" effect seen in the optical. At optical maximum the UV spectrum of UX Ori is dominated by heavy line blanketing from accreting circumstellar gas with velocities as high as +200km/s. …
The far UV variability of the symbiotic star SY Muscae.
Pereira, C. B.; Vogel, M.; Nussbaumer, H.
SY Muscae is a symbiotic star. Its periodic luminosity variation has been followed since the beginning of this century. No outburst or erratic variation has ever been seen. Its light variation is ascribed to eclipses within a binary system. We present FUV observations taken by IUE from 1981 to 1993. These spectra confirm the binary interpretation.…
Cometary breakup calculations based on a gravitationally-bound agglomeration model: the density and size of Shoemaker-Levy 9.
Solem, J. C.
By modeling Comet Shoemaker-Levy 9 (1993e) as an agglomeration of identical spherical components, bound together only by gravitation, I obtain several qualitative and quantitative features of the comet's breakup during its close encounter with Jupiter. By comparing the size, number, and spatial distribution of the calculated cometary fragments wit…
Construction of the intermediate HIPPARCOS astrometric catalogue
Lattanzi, M. G.; Lindegren, L.; Mignard, F. +15 more
The data analysis methods for the determination of the astrometric parameters from observations by the Hipparcos satellite as used in FAST and NDAC consortia for the construction of intermediate 18-month and 30-month solutions are presented. The quality of the results depends upon calibrations of the instrumental parameters, examples of which are …
On the relative luminosities of the stars in the Wolf-Rayet binary V444 Cygni.
Koenigsberger, G.; Cherepashchuk, A. M.; Moffat, A. F. J. +1 more
A new spectroscopic estimate of the luminosity ratio q=L_WR_/L_O6_ is obtained from the dilution of the absorption lines of the O6V-III component in the WR eclipsing binary V444 Cygni (WN5+O6). We find q=0.60+/-0.06 for the range λλ4000-6000A and q=0.56+/-0.13 from IUE spectra. This clearly indicates that the light of the O6 dominates the combined…
The ultraviolet properties of cool material ejected by hydrogen-deficient stars.
Jeffery, C. S.
Carbon-rich H-deficient stars which shed dusty material in the line-of-sight exhibit RCrB-like optical variations. The UV extinction toward several such objects differs significantly from the average interstellar extinction law; these data have been re-examined. The observed peak in extinction at 4.1µm^-1^(=240nm) has previously been explain…