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VLBI and Optical Astrometry of Southern Extragalactic Radio Sources and Radio Stars
White, Graeme L.; Jauncey, David L.; Lestrade, Jean-Francois +3 more
Mark III very long baseline interferometry (VLBI) has been used to determine the positions of ten compact extragalactic radio sources in the southern hemisphere. These positions are relative to the Jet Propulsion Laboratory VLBI celestial reference frame and are accurate at the 0.01" level, more than an order of magnitude improvement compared to t…
Spectroscopic binary orbits from ultraviolet radial velocities. Paper 6: Gamma 2 Velorum
Stickland, D. J.; Lloyd, C.
Off-nucleus IUE observations of NGC 1275.
Norgaard-Nielsen, H. U.; Jorgensen, H. E.; Hansen, L.
We have mapped the brightest parts of the two velocity systems of ionized gas in NGC 1275 with IUE. We have detected extended Lyα and an UV continuum at several positions. The Lyα emission originates from the low velocity system and, we argue, probably also the UV continuum. The UV continuum is consistent with star bursts with ages <= 2 10^7^ y…
Hydrogenated Amorphous Carbon Grains in Comet Halley?
Colangeli, L.; Fonti, S.; Bussoletti, E. +3 more
Recent IR observations of Comets Halley, Wilson, and Bradfield have shown the existence of an emission feature falling at around 3.4 microns. In this paper, it is shown that a good fit of both the IR continuum and the band can be obtained by assuming a simple thermal emission model based upon the optical properties of hydrogenated amorphous carbon…
Coordinated Optical and Ultraviolet Observations of DH Leo
Huenemoerder, David P.; Buzasi, Derek L.; Ramsey, Lawrence W. +4 more
Results are reported from contemporaneous KPNO optical spectroscopy, IUE UV spectroscopy, and KPNO R photometry of the DH Leo triple system in spring 1987. The data are presented in tables, graphs, and spectral phase images and discussed in detail. The H-alpha, H-beta, H-gamma, H-delta, and Ca II H and IRT lines are found to have excess emission, …
Extinction-independent determination of temperatures for central stars of planetary nebulae.
Grewing, M.; Neri, R.
A method to determine temperatures for central stars of planetary nebulae from ultraviolet color indices which are essentially extinction-independent is described and applied. Using a standard extinction law (Seaton, 1979) and assuming that the continuum emission from the nuclei of planetary nebulae can be approximated by black-body distributions,…
Activity in late-type stars. V. Rotational modulation and flaring in UV lines on the most rapidly rotating dMe star, GL 890 (BD -16 6218).
Byrne, P. B.; McKay, D.
A series of UV spectra of GI 890 taken at two epochs separated by more than two years (on October 11-13, 1984 and on December 26, 1986) where obtained by the IUE satellite and using both the spectrograph's short-wavelength and long-wavelength cameras. Based on these data, the energy balance in the star's magnetically heated chromosphere and the tr…
The Orbit and Colors of the Cepheid S MUSCAE
Evans, Nancy Remage
A new orbit has been computed for the binary Cepheid S Mus combining new data from Mount John Observatory with previous data. Corrections to the colors and reddening due to the light from the companion are derived. The spectral type determined from IUE low-dispersion spectra is used for these corrections. The corrections are small, even though the…
Self-consistent comptonized models for the spectra of low-mass X-ray binaries.
Ross, R. R.; Ponman, T. J.; Foster, A. J.
We have constructed Comptonized spectral models and fitted them to EXOSAT spectra of eleven bright low-mass X-ray binaries. The models are based on the premise that these systems contain circumstellar material which modifies the X-ray spectrum passing through it. We idealize this situation as a point source of X-rays, the neutron star, embedded in…
A computed spectrum for the normal star ι Herculis (B3 IV) in the region 122.8 - 195.0 nm.
Bonifacio, P.; Castelli, F.
The authors have compared Copernicus and IUE high resolution spectra of the sharp-lined normal star ι Her with an LTE synthetic spectrum computed by using a blanketed Kurucz's (1979) model with parameters Teff = 17180K, log g = 3.43, and the new line lists of Kurucz (1988). A microturbulence ξ = 0 km s-1 gives the best agreem…