Search Publications
Quasi-simultaneous ultraviolet and optical observations of PKS 2155-304 = H 2155-304.
Maraschi, L.; Tanzi, E. G.; Tarenghi, M. +1 more
The BL Lac object PKS 2155-304 was repeatedly observed in the 1200-3000 Å band with the International Ultraviolet Explorer. The variability of the source in this band is studied in detail. The UV continua are well fitted by power laws with frequency spectral index αν varying between -0.7 and -0.9. An optical spectrum was taken within on…
Galactic gamma radiation : the contribution from discrete sources.
Houston, B. P.; Wolfendale, A. W.
The contribution from discrete sources to the emission of galactic gamma rays is studied based on an analysis of the SAS II satellite data. The data are analyzed using cross-correlation techniques, and the results are interpreted using extensive Monte-Carlo simulations of the gamma-ray sky. These results are compared to earlier analyses based on t…
The LMC emission line star S 22 (=HD 34664). III. Ultraviolet to infrared energy distribution.
Friedjung, M.; Viotti, R.; Muratorio, G. +1 more
New observations of the superluminous star S22 in the Large Magellanic Cloud obtained with the ultraviolet satellite IUE and in the infrared are discussed. The low resolution ultraviolet spectrum is dominated by Fe II emission and absorption lines, probably formed in an expanding cool circumstellar envelope. An attempt was made to synthesize the U…
Non-LTE analysis of subluminous O-stars. V. The binary system HD 128220.
Kudritzki, R. P.; Gruschinske, J.; Simon, K. P. +2 more
Spectra of the binary system HD 128220 were taken in the UV and in the visual. The hot component - an O subdwarf - is analysed by means of non-LTE calculations. The cool companion has an effective temperature about 5500 ± 500K (Type G). The discussion of the stellar parameters arrives at results which agree with those derived from the mass functio…
Boss 1985 : mass loss investigation based on IUE spectra.
Reimers, D.; Che, A.
From recent IUE observations of Boss 1985 - a VV Cep type spectroscopic binary - the authors deduce the mass loss rate of the primary M star using a non-spherical three-dimensional line transfer code applied on Fe II UV mult. 9 lines. Best agreement between observed and computed line profiles is obtained using wind velocity of 10±5 km s-1
ESO 438 -G 9 : a Seyfert galaxy with unusual properties.
Kollatschny, W.; Fricke, K. J.
The authors discuss optical and UV spectroscopic data of the 1.5 Seyfert galaxy ESO 438-G9 found from a survey of barred galaxies. Its spectrum shows strong Fe II emission. A very steep continuum gradient in the UV is reflected in the absence of higher ionization lines. A double absorption feature is present shortward of the Hα and Hβ emission lin…
IUE observations of the eclipsing binaries TV CAS and YZ Cas.
de Landtsheer, A. C.; Mulder, P. S.
Two high resolution IUE spectra of the primaries of the eclipsing binaries TV Cas and YZ Cas are used to derive iron group abundances. YZ Cas shows clear metallicity effects (Fe is 6 times over abundant), while TV Cas does not. The metals in YZ Cas add up to a Z value of over 0.03. The microturbulent velocities are 6.5 km s-1 (TV Cas) a…
The temperature of the pulsating DB white dwarf GD 358.
Koester, D.; Weidemann, V.; Vauclair, G.
IUE observations of the DB white dwarf GD 358, which has recently been shown to be pulsating, combined with an evaluation of multichannel photometry demonstrate that this star has an effective temperature of about 26000 + or - 2000 K. This is considerably higher than predicted by Winget et al. (1982), but is still in qualitative agreement with pul…
A search for UV-line profile variability in five 0-stars.
Kontizas, M.; Franco, M. L.; Kontizas, E. +1 more
Five O-stars have been monitored with IUE in the far-UV, at high resolution, to study resonance line profile variability. The O-type stars Zeta Pup, 9Sgr, HD 175754, Lambda Ori A, and HD 105056 have strong stellar winds. Their resonance line profiles of N V, Si IV, and C IV ions, observed at different epochs since May 1978, have been compared in t…
IUE observations of high velocity interstellar gas tentatively associated with Radio Loop II.
Keenan, F. P.; Bates, B.; Giaretta, D. L. +1 more
Red-shifted high velocity gas components (HVC) have been positively detected in IUE spectra of six out of a sample of eleven selected stars across a region of sky of some 40°. Properties of the HVC determined from the spectra of three stars indicate that the material is cool gas with a density nH ≈ 100 cm-3 and thickness ≈0.1…