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The three-ring structure of Supernova 1987A

Burderi, L.; King, A. R.

The current scenario for the complex <=3-arcsec structures surrounding SN 1987A is that they result from the emission of a thin shell of matter surrounding the supernova, illuminated by the initial extreme-ultraviolet flash from the explosion of the progenitor. Before the Hubble Space Telescope (HST) the two ring-shaped loops, ~3 arcsec in size…

WFPC2 Images of Multiple Nuclei in Nearby Active Galactic Nuclei

Gorjian, Varoujan

High-resolution images have been made with the Hubble Space Telescope of the cores of three active galaxies: Mrk 348, Mrk 516, and Mrk 789. The 500 s images were taken using the WFPC2 camera with the F606W filter. Each galaxy exhibits structure which may be interpreted as multiple nuclei. Mrk 348 appears to have two nuclei, although it is possible…

ULYSSES energetic ion observations during the declining phase of solar cycle 22

Sanderson, T. R.

The Ulysses spacecraft was launched in October 1990, just after the maximum of solar cycle 22. Part of the journey to Jupiter was during one of the most active periods of solar activity recorded so far. Solar activity remained exceptionally high for many months after launch, solar energetic particles dominating the particle observations at Ulysses…

The First Search for a Gamma-Ray Burst Quiescent Counterpart in the Extreme Ultraviolet with EUVE

Hurley, K.; Kouveliotou, C.; Li, P. +3 more

The opening of the extreme ultraviolet window by the Extreme Ultraviolet Explorer (EUVE) satellite has provided the unique opportunity to perform the first search for a quiescent gamma-ray burst counterpart at these wavelengths. Such emission might be expected if some bursts are related to nearby hot neutron stars or neutron stars with accretion d…

Galactic Cosmic Ray Propagation at Low Energies: The Interstellar Medium and Partial Cross Sections

Thayer, M. R.

Schmidt plate astrometric reductions using preliminary HIPPARCOS and TYCHO data

Makarov, V. V.; Evans, D. W.; Bastian, U. +9 more

New reductions of Schmidt plate measurements have been performed, using preliminary Hipparcos and Tycho data for the astrometric reference stars. The measurements reported here have been obtained with the MAMA automatic measuring machine of the Centre d'Analyse des Images in Paris. The Hipparcos data considered, the `combined 30-month solution', o…

Blue stragglers and horizontal branch stars in the core of the globular cluster M3.

Burgarella, D.; Paresce, F.; Quilichini, V.

The core of the Galactic globular cluster Messier 3 (NGC 5272) has been imaged through the f/96-F140W, f/96-F220W and f/96-F346M ultraviolet filters of the Faint Object Camera onboard the Hubble Space Telescope (HST) down to an ultraviolet magnitude of ~20. We measure a high specific frequency of blue stragglers stars (BSS), f_BSS_=0.29 in the obs…

UV Spectrophotometry of the Hottest Stars from the Southern HK Survey

Beers, Timothy C.; Drilling, John S.

Low-resolution UV spectra have been obtained with the long- and short-wavelength lUE cameras for seven of the hottest stars identified in the ongoing HK objective-prism/interference-filter survey begun by Beers, Preston, & Shectman. These stars are a subset of a sample of some 25,000 stars at high galactic latitude whose objective-prism spectr…

Is this orbit really necessary? III. On the use of Hipparcus double-star measurements for orbit computation.

Dommanget, J.

In this paper the advisability of computing some double star orbits is discussed. As a conclusion, it appears that the Hipparcos double star measurements of relative positions will not essentially contribute to an improvement in our knowledge of double star orbits.

Structure of mass-loading shocks. 2. Comparison of theory and observation at comet Halley

Coates, A. J.; Neubauer, F. M.; Reme, H. +2 more

The multifluid diffusive model of G. P. Zank et al. (1994), which describes the interaction of the solar wind with a cometary plasma in the outer coma, has been used to model the structure of the Halley bow shock. The theoretical results are compared to in situ observations made by Giotto. We compare the solar wind and cometary ion number densitie…