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Outbursts by Low-Mass White Dwarfs in Symbiotic Variables
Sion, Edward M.; Ready, Christian J.
We have investigated the nature of P Cygni-like features in the high resolution IUE spectra of the symbiotic variables BF Cyg and EG And by looking for orbital phase-dependent variations in the structure and velocity of the C IV (1550 A) resonance doublet in 10 archival IUE high-dispersion spectra of these systems and by comparing their profiles w…
Imaging of Four Planetary Nebulae in the Magellanic Clouds Using the Hubble Space Telescope Faint Object Camera
Boksenberg, A.; Barbieri, C.; Weigelt, G. +18 more
Using the Faint Object Camera on-board the Hubble Space Telescope, we have obtained images of four planetary nebulae (PNe) in the Magellanic Clouds, namely N2 and N5 in the SMC and N66 and N201 in the LMC. Each nebula was imaged through two narrow-band filters isolating [O III] λ5007 and Hβ, for a nominal exposure time of 1000 s in each filter. Si…
The origin of the X-ray emission in 3C 273 and 3C 120.
Walter, R.; Courvoisier, T. J. -L.
We present an analysis of simultaneous X-ray and ultraviolet observations of the two quasars 3C 273 and 3C 120 which exhibit very similar multi-waveband spectra. This investigation is limited to the long term variations observed in the two spectral bands and to their correlations. In both objects, the X-ray and ultraviolet lightcurves are not coup…
Ulysses observations of escaping VLF emissions from Jupiter
MacDowall, R. J.; Kaiser, M. L.; Desch, M. D. +5 more
The Ulysses URAP experiment has detected Jovian radio emissions in the VLF range at distances from Jupiter in excess of 1.5 A.U. The URAP observations represent the first synoptic observations of Jupiter in the VLF band, 3 to 30 kHz. In this band lie the low-frequency extent of the bKOM emission, the escaping continuum emission, and the Jovian typ…
Ultraviolet and optical spectra of central stars of halo planetary nebulae.
Pena, M.; Torres-Peimbert, S.; Ruiz, M. T.
UV and optical spectrophotometric data on central stars of eight Population II planetary nebulae are analyzed. Visual magnitudes, spectral classification, color temperatures, and luminosities are derived from these data. All the stars in the sample exhibit an absorption-type spectrum, and most of them have normal H and He photospheric abundances, …
Quasi-linear velocity space diffusion of heavy cometary pickup ions on bispherical diffusion characteristics
Coates, A. J.; Johnstone, A. D.; Huddleston, D. E.
We consider an ion transport equation describing the source, convection, adiabatic acceleration, and quasi-linear velocity diffusion of cometary pickup ions. The equation is solved numerically along solar wind plasma flow lines for the environment of comet Halley, to obtain distributions at positions on the Giotto spacecraft trajectory which may b…
IR survey of OB emission-line stars in the SMC : detection of a new B E supergiant, AV 172.
Stahl, O.; Zickgraf, F. -J.; Wolf, B.
We surveyed bright SMC emission-line stars in the infrared (JHK) in order to search for more B[e] supergiants in this galaxy by means of their IR excesses. One new star, AV 172, with the B [e] type IR excess was detected. Optical and IUE spectroscopy of this star showed it to be a B8 [e]Ib supergiant. Our survey showed that in the SMC four B [e] s…
Beta Pictoris and the lambda Bootis stars : testing the accretion hypothesis.
King, Jeremy R.; Patten, Brian M.
It is suggested that Beta Pic may be an unrecognized Lambda Boo star, based on the recent discussion of its evolutionary status by Paresce and the proposal by Venn and Lambert linking circumstellar material with the Lambda Boo phenomenon. The star's metallicity, photometric indices and UV spectrum support this interpretation. If confirmed as a Lam…
In ecliptic observations of Jovian radio emissions by Ulysses comparison with Voyager results
MacDowall, R. J.; Kaiser, M. L.; Desch, M. D. +6 more
During the Ulysses inbound cruise to Jupiter the Unified Radio and Plasma Wave (URAP) experiment observed a variety of the planet's radio components in the frequency range below 1 MHz. Most of these emissions were already detected by the Voyager Radio Astronomy (PRA) and Plasma Wave (PWS) experiments, however with much less sensitivity and differe…
Positions and parallaxes from the HIPPARCOS satellite - A first attempt at a global astrometric solution
Lindegren, L.; van Leeuwen, F.; Perryman, M. A. C. +2 more
The last stage of the basic astrometric reduction of Hipparcos data is to combine angular measurements along great-circle scans into a globally coherent system of positions, proper motions and trigonometric parallaxes. We report the results of a first attempt at such a 'sphere solution' of positions and parallaxes using great-circle results calcul…