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The spectrum of the planetary nebula NGC 6886
Hyung, Siek; Aller, Lawrence H.; Keyes, Charles D.
The relatively young, high-excitation planetary nebula (PN) NGC 6886 shows a remarkable variety of lines from both high- and low-excitation stages, i.e., from N^0 to N^4+, and as a result it provides unique opportunities for detailed studies of physical processes, using a theroetical model. By combining Hamilton echelle observations with UV data s…
Dispersion of electrostatic waves in the Io plasma torus and derived electron temperature
Moncuquet, M.; Meyer-Vernet, N.; Hoang, S.
We present a detailed analysis of the set of radio spectra acquired during the Ulysses spacecraft passage through the outer part of the Io plasma torus (at ~8 RJ). Since Ulysses is the first spacecraft to explore the torus far from the equator and the onboard plasma analyzers were shut off, these wave data are the only ones providing an…
Anisotropy of inertial range turbulence in the polar heliosphere
Balogh, A.; Horbury, T. S.; Forsyth, R. J. +1 more
A variance analysis of high frequency, inertial range fluctuations in the polar magnetic field as recorded by the Ulysses spacecraft indicates that they are largely transverse to the ambient magnetic field direction and highly anisotropic. Despite large changes in the mean field direction caused by the presence of large amplitude Alfvén waves, ali…
Spectral analysis of the hot DO white dwarf PG1034+001.
Werner, K.; Dreizler, S.; Wolff, B.
We present a non-LTE model atmosphere analysis of the hot DO white dwarf PG1034+001. It is based on archival HST GHRS spectra, on new optical medium resolution spectra and pointed ROSAT PSPC observations. The effective temperature is higher than previously thought (T_eff_=100000K, Logg=7.5). We determined abundances of carbon, nitrogen, and oxygen…
Time-dependent Behavior and Physical Conditions of the LMC Planetary Nebula N66
Pena, M.; Torres-Peimbert, S.; Ruiz, M. T. +2 more
Optical and UV spectrophotometric data for the planetary nebula N66 in the Large Magellanic Cloud gathered in the 1987-1994 interval are analyzed. The central star, which had a featureless weak continuum, has developed intense W-R features and P Cygni profiles that were not present before 1990. He- and N-rich material, processed during the CNO cyc…
Simultaneous observations of the Saturnian aurora and polar haze with the HST/FOC
Waite, J. H.; Grodent, D.; Gladstone, G. R. +3 more
Near simultaneous observations of the Saturnian H2 north ultraviolet aurora and the polar haze were made at 153 nm and 210 nm respectively with the Faint Object Camera on board the post-COSTAR Hubble Space Telescope. The auroral observations cover a complete rotation of the planet and, when co-added, they reveal the presence of an auror…
Solar wind helium isotopic composition from SWICS/ULYSSES
Bochsler, P.; Geiss, J.; Gloeckler, G. +2 more
This is the first study of the isotopic composition of solar wind helium with the SWICS time-of flight mass spectrometer. Although the design of SWICS is not optimized to measure3He abundances precisely,4He/3He flux ratios can be deduced from the data. The long term ratio is 2290±200, which agrees with the results …
The Binary Double-degenerate Nature of the Bright DAO White Dwarf Feige 55
Barstow, M. A.; Holberg, J. B.; Saffer, Rex A. +1 more
Recent IUE and optical spectra of the bright DAO white dwarf Feige 55 reveal large Doppler shifts due to orbital motion. These Doppler shifts have a period of 1.49303 +/- 0.00011 days with a semi-amplitude of 77.4 +/- 7.0 km s-1. There is no strong photometric signature of any companion; J- and K-band photometry place an upper limit of 0.1 M⊙ on t…
The β Pictoris circumstellar disk. XVII. Physical and chemical parameters of the disk.
Deleuil, M.; Ferlet, R.; Vidal-Madjar, A. +3 more
New high resolution spectroscopic observations in the visible as well as archival HST UV data are used to investigate some physical and chemical properties of the disk around β Pictoris . A number of circumstellar lines are detected for the first time: Fe I , as well as weak lines of Fe II , Mn II and Zn II . Reliable estimates of the total gaseou…
New global solution of Earth orientation parameters from optical astrometry in 1900-1990.
Pesek, I.; Vondrak, J.; Ron, C. +1 more
Astrometrically observed variations of latitude and Universal time with thirty instruments of different types, located at 19 observatories all over the world, are used to derive polar motion, UT1-TAI (since 1956) and celestial pole offset at 5-day intervals. The values based on the observations of individual stars are used, the model of least-squa…