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Impact of Comet Shoemaker-Levy 9—Size, Origin, and Plumes: Comparison of Numerical Analysis with Observations

Takata, Toshiko; Ahrens, Thomas J.

Numerical results of impact of Comet Shoemaker-Levy 9 (SL9) on Jupiter are compared with observational phenomena to investigate the size and origin of SL9 and impact features. Plume evolution is simulated numerically for 0.4- and 2.0-km-diameter (D) impactors. Analytical estimates indicate that the maximum plume heights are proportional to (D/lnD)…

Spectroscopic bianry orbits from ultraviolet radial velocities. Paper 26: HD 165052

Stickland, D. J.; Lloyd, C.; Koch, R. H.

The IUE Spectrum of the Binary Nucleus of the Planetary Nebula NGC 1514

Feibelman, W. A.

Archival IUE low-dispersion spectra and the first ultraviolet high-dispersion spectrum of the binary nucleus of NGC 1514 have been analyzed. Both SWP and LWR low-dispersion spectra show variability by as much as a factor of two in the continuum level between the years 1978 and 1989. Weak P Cygni features for OV lambda 1371 and C IV lambda 1549 yie…

The close DAO+dM binary RE J0720-318: a stratified white dwarf with a thin H layer and a possible circumbinary disk.

Barstow, M. A.; Burleigh, M. R.; Dobbie, P. D.

We have analysed the EUVE spectrum of the DAO white dwarf RE J0720-318. In contrast to the optical spectrum, which can only be fitted with a homogeneously mixed H+He atmosphere, we find the EUVE spectrum can only be matched with a stratified structure. The H layer mass of 3x10^-14^M_[sun}_, is a factor of ~10 below upper limits from previous EUVE …

Comet halley's nucleus: A physical interpretation

Keller, H. U.; Thomas, N.

The nucleus of comet Halley was the first to be detected and observed by cameras on board spacecraft during the fly-bys in 1986. The interpretation of both these observations and of the results from other experiments as well as many subsequent corroborative measurements of comet Halley and of other comets are reviewed. Cometary nuclei are relative…

The Ultraviolet Spectrum of the Magnetic Cataclysmic Variable RX J1802.1+1804

Singh, K. P.; Shrader, C. R.; Barrett, P.

We observed the counterpart to the X-ray source RX J1802.1+1804, an object recently discovered as part of a survey to identify the optical counterparts to ultrasoft X-ray sources in the ROSAT point-source catalog that was subsequently identified as a magnetic cataclysmic variable, with the ultraviolet spectrometers on IUE in low dispersion mode. W…

HIPPARCOS extragalactic link by means of absolute proper motions of stars related to galaxies: Kyiv solution.

Rybka, S. P.; Yatsenko, A. I.; Kharchenko, N. V. +1 more

Absolute proper motions of stars with respect to galaxies obtained within the KSZ and MEGA programmes were used in the determination of spin parameters of the Hipparcos catalogue system relative to the inertial reference frame. The Kyiv part of the Bonn-Potsdam-Kyiv project "Hipparcos extragalactic link by photographic astrometry" is discussed. So…

IUE observations of Beryllium II lines in Lithium-rich giant stars.

de Medeiros, J. R.; Monier, R.; Lebre, A. +1 more

IUE spectra of the Beryllium II region are presented for two Lithium-rich giant stars, HD 9746 and HD 112127. In either spectrum there is no sign of significant Beryllium features at the BeII lines 3130.416Å or 3131.064Å, which seems to indicate that Be was depleted in these two Lithium-rich giants. This suggests that some additional Lithium was p…

Hot Evolved Objects in Different Parent Galaxies: The Stellar Winds of Three Planetary Nebula Nuclei in the Large Magellanic Cloud

Bianchi, Luciana; Vassiliadis, Emanuel; Dopita, Michael

Three planetary nebulae in the Large Magellanic Cloud (LMC) were observed with the Faint Object Spectrograph on board the Hubble Space Telescope. Their central stars display P Cygni-like features in the ultraviolet. We modeled these profiles to derive the stellar wind velocities. The wind velocities of the LMC planetary nebula nuclei (PNNs) are co…

Hubble Space Telescope Spectroscopy of the Carbon Star TX Piscium

Robinson, Richard D.; Johnson, Hollis R.; Querci, Francois +5 more

Ultraviolet spectra obtained with the Hubble Space Telescope of the carbon star TX Piscium (HR 9004) are presented, along with analysis providing information on its outer atmosphere, including flow and turbulent velocities, line formation mechanisms, and variations with time. Both thermal (collisionally excited) and fluorescent emission from the c…