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Ultraviolet observations of Chiron with the HST/FOS: Examining a Centaur's Gray Matter
Parker, Joel Wm.; Stern, S. Alan; A'Hearn, Michael F. +2 more
We present ultraviolet (UV) observations of Chiron during two epochs using the Hubble Space Telescope / Faint Object Spectrograph (HST/FOS). The first observations (1996 Jan 23-24 UT) were made 3 weeks before Chiron's perihelion, and include a series of seven spectra obtained over 3.9 hours. A single follow-up observation was made 3 months later (…
The vertical disc structure of U Geminorum in outburst
Naylor, T.; La Dous, C.
We have obtained phase-resolved UV spectroscopy from the International Ultraviolet Explorer, and V-band CCD photometry of U Gem in outburst. Our data show little or no orbital modulation outside eclipse, in contrast to the X-ray light curves during outburst, which show large dips. We find that a consistent model of the optical, UV and X-ray light …
The Trigonometric Parallax of the Hyades Cluster
van Altena, W. F.; Lee, J. T.; Hoffleit, E. D.
The recent completion of the Fourth Edition of the General Catalogue of Trigonometric Parallaxes (YPC) has enabled us to redetermine the trigonometric parallax of the Hyades Cluster based on individual measurements of the cluster member stars. Since the YPC has been carefully evaluated and corrected for systematic errors in both the absolute paral…
Searching for chromospheric Lyman-α emission in A-F stars from IUE high resolution spectra.
Talavera, A.; Freire Ferrero, R.; Bruhweiler, F. +3 more
With the aim of locating the boundary for the onset of chromospheric emission in the H-R diagram we have undertaken a spectroscopic study of the hydrogen Ly-α, using the IUE short wavelength spectrograph in the high resolution mode. We report here on the analysis of IUE spectra of 11 A-F type stars. We have detected Ly-α emission in stars as early…
Self-consistent and Time-dependent Solar Wind Models
Rosner, R.; Suess, S. T.; Musielak, Z. E. +2 more
We describe the first results from a self-consistent study of Alfvén waves for the time-dependent, single-fluid magnetohydrodynamic (MHD) solar wind equations, using a modified version of the ZEUS MHD code. The wind models we examine are radially symmetrical and magnetized; the initial outflow is described by the standard Parker wind solution. Our…
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…