Search Publications

The Chemical Evolution of the Galactic Disk - Part One - Analysis and Results

Gustafsson, B.; Andersen, J.; Lambert, D. L. +3 more

The ultraviolet to soft X-ray bump of Seyfert 1 type active galactic nuclei.

Walter, R.; Fink, H. H.

The soft X-ray (0.1 - 2.4 keV) emission of 58 Seyfert type active galactic nuclei have been studied using the spectra obtained during the ROSAT all sky survey. These spectra are well represented by power law models with photon indices ranging between 1.6 and 3.4. The spectra usually do not show intrinsic absorption. A notable exception is Mrk 766 …

Elemental abundances in normal late-B and HgMn stars from co-added IUE spectra. I. Iron-peak elements.

Dworetsky, M. M.; Smith, K. C.

The abundances of five iron-peak elements (chromium through nickel) in a sample of forty normal, superficially normal, and HgMn-type late-B stars are derived by spectrum-synthesis analysis of co-added high-resolution International Ultraviolet Explorer (IUE) spectra. Approximately solar abundances of these elements are obtained for the normal stars…

A model for the 89 Herculis system.

Waters, L. B. F. M.; Mayor, M.; Trams, N. R. +1 more

We report new radial velocity measurements of the F2 supergiant 89 Her that confirm the binary nature of this star. A period search yields an orbital period of 288.4 +/- 0.7 days, in close agreement with earlier results. We also present intermediate resolution spectra in the wavelength range 3500 - 11,000 A, with numerous emission lines. We use th…

On the relative C,N,O abundances and the evolutionary status of yellow symbiotic stars.

Nussbaumer, H.; Schmid, H. M.

Symbiotic binaries consist of a cool giant and a hot radiation source, which is ionizing the nebula associated with the system. Yellow symbiotic stars can be divided according to their IR colors into s-type (stellar) and d'-type (dust) systems. The s-types are relatively narrow systems, with orbital periods of several hundred days. They contain hi…

Optical/UV counterpart of the supersoft transient X-ray source RX J0513.9-6951 in the Large Magellanic Cloud.

Motch, C.; Bianchi, L.; Pakull, M. W. +5 more

Optical and IUE observations of the ROSAT X-ray transient RX J0513.9-6951 show this object to be remarkably similar to Cal 83, the prototype of luminous supersoft sources which is also located in the LMC. The counterpart is a B ~ 17 mag blue star which apparently did not vary much around the time of the X-ray outburst. Spectrophotometry reveals na…

SAO 244567 : a post-AGB star which has turned into a planetarey nebula within the last 40 years.

Pottasch, S. R.; Clavel, J.; de Martino, D. +5 more

SAO 244567 (Hen 1357 = CPD -59 deg 6926 = IRAS 17119-5926) is an IRAS source with far infrared colors and flux distribution similar to those of planetary nebulae. The IUE ultraviolet spectra obtained in July 1988 and April 1992 show nebular emission lines, and also the changes in the spectra suggest the formation of the planetary nebula and the ra…

Lyman-alpha emission in spectra of Herbig AE stars. an indication of accretion ?

Talavera, A.; Blondel, P. F. C.; Djie, H. R. E. T. A.

Lyman-alpha emission lines have been detected in the IUE spectra of several Herbig Ae stars, but not in those of Herbig Be stars. The shapes and positions of these lines are not consistent with those expected from a chromosphere and transition region (TR), which may be the origin of the other FUV emission lines in the spectra of these stars. The c…

Environment dependence of interstellar extinction curves.

Greenberg, J. M.; Jenniskens, P.

The IUE interstellar extinction curves published by Aiello et al. (1988) are decomposed into a bump, linear rise and FUV non-linear rise, in the parameterization scheme of Fitzpatrick & Massa (1990). The parameters of the 115 extinction curves are given. The lines of sight are characterized from the IRAS Skyflux and Point Source Catalogue data…

UES and IUE observations of the O9.5V star HD 93521 : non-radial pulsatutions, wind and distance.

Howarth, Ian D.; Reid, Andy H. N.

We have obtained time-series spectroscopy of the rapidly rotating O9.5 V star HD 93521 during commissioning of the Utrecht Echelle Spectrograph (UES) on the William Herschel Telescope. The He I lines show 'wiggles' at the approximately 1% level, which move systematically from blue to red across the profile; by contrast, the He II lines do not show…