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Stellar activity and the Wilson-Bappu relation.
Engvold, O.; Elgaroy, O.; Joras, P.
The MgII h and k lines of 78 single stars observed with the International Ultraviolet Explorer (IUE) observatory have been analyzed. Stars of spectral classes F, G, K and M and luminosity classes I-V are represented in the sample. From these data it is shown that the Wilson-Bappu relation for the Mg II h and k lines is fulfilled over a range of 18…
Detectability of High-Redshift Elliptical Galaxies in the Hubble Deep Field
Maoz, Dan
Relatively few intensively star-forming galaxies at redshifts of z>2.5 have been found in the Hubble Deep Field (HDF). This has been interpreted to imply a low space density of elliptical galaxies at high z, possibly due to a late (z<2.5) epoch of formation or to dust obscuration of the ellipticals that are forming at z~3. I use Hubble Space…
Ulysses solar wind plasma observations at high latitudes
McComas, D. J.; Goldstein, B. E.; Bame, S. J. +7 more
Ulysses reached its peak northerly heliolatitude of 80.2 degN on July 31st, 1995, and is now moving towards aphelion at 5.41 AU which it will reach in May, 1998. We summarize measurements from the solar wind plasma experiment, SWOOPS, emphasizing northern hemispheric observations but also providing southern and equatorial results for comparison. T…
Abundances and Depletions toward the Orion Nebula
Snow, Theodore P.; Shuping, R. Young
This paper presents an absorption-line study of θ1 C Orionis (HD 37022), based on IUE data. The line of sight, as determined by O'Dell et al. (1993), is thought to consist of two major cloud complexes: the ``neutral lid'' and some foreground material. A key challenge was to improve the S/N for IUE spectra, and this is discussed in some …
Observations of the wind of the old nova V603 Aquilae with the HST-GHRS.
Selvelli, P.; Friedjung, M.; Cassatella, A.
High resolution spectra of the old nova V603 Aql (1918) were taken in the regions of the C IV, N V and Si IV resonance doublets, using the G160M grating of the GHRS on board the Hubble Space Telescope. No sign of sharp absorption components due to the envelope ejected in 1918 is present. If spherical symmetry is assumed, the estimated upper limits…
The early-type binary KX Velorum.
Drechsel, H.; Lorenz, R.; Mayer, P.
A spectroscopic study of the double-lined OB-type binary system KX Vel is presented. Radial velocities were measured on 20 new CCD spectra and 4 high dispersion IUE SWP images. From a combination with early photographic data, the orbital period was found to be 26.306d. The high precision radial velocity curve of the evolved primary component allow…
Ongoing Mass Ejection in the Peculiar, Hot Do Degenerate KPD 0005+5106
Sion, Edward M.; Barstow, Martin A.; Holberg, Jay B. +1 more
We present an analysis of four high-resolution far-ultraviolet spectra of the hot, peculiar DO white dwarf KPD 0005+5106 obtained with short-wavelength prime (SWP) spectrograph aboard the International Ultraviolet Explorer (lUE) spacecraft. These spectra reveal weak, probably variable, peculiar absorption and emission transitions of ultrahigh exci…
An Explanation of the ROSAT High-Resolution Imager Ultraviolet Sensitivity
Murray, S. S.; Barbera, M.; Collura, A. +1 more
The UV sensitivity to bright stars observed during operations of the high-resolution imager (HRI) on the X-ray-XUV Roentgen Satellite (ROSAT) has been commonly interpreted as a result of enhanced transmission solely in the wavelength range 1500-1700 Å of the HRI's UV/ion shield. We report on recent laboratory UV transmission measurements of HRI fl…
3C 254: the alignment effect and unification schemes
Bremer, M. N.
3C 254 is a radio-loud quasar at z=0.734. Optical line and continuum emission from the underlying galaxy is clearly extended and aligned with the radio axis; the object shows the so-called `alignment effect' which is often seen in powerful radio galaxies. This is the clearest case yet of the continuum alignment effect in a radio-loud quasar. The o…
Optical and UV observations of the BL Lacertae object PKS 2155-304.
Wagner, S. J.; Heidt, J.; Wilhelm-Erkens, U.
The BL Lac object PKS 2155-304 has been monitored in two subsequent observing campaigns within three weeks in June 1990 and during another run in September 1994 at optical wavelengths. During the first part PKS 2155-304 showed night-to-night variations of a few percent, whereas in the second part no variability could be detected. During the third …