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The Density Profile of 47 Tucanae

Paresce, Francesco; Gilliland, Ronald L.; Bohlin, Ralph C. +2 more

We have used high-resolution HST-WF/PC images of the core of the globular cluster 47 Tucanae in the U-band to determine its radial density profile. The exceptional photometric quality of the data set ensures highly reliable measurements since no photometric completeness correction is required for stars at and above the turn-off luminosity over the…

Very small grain emission in NGC 7023.

Walker, H. J.; Lemke, D.; Schulz, B. +10 more

We observed the reflection nebula NGC 7023 at various positions using wide and narrow band photometry centred on the 7.7 and 11.3µm PAH emission features and wide band photometry at 20 and 25µm. No significant variations have been detected over the nebula in the 7.3 and 20µm continuum relative to the total emission in the 6-15&mi…

Theoretical Plasma Distributions Consistent with ULYSSES Magnetic Field Observations in a Solar Wind Tangential Discontinuity

Tsurutani, B. T.; Roth, M.; De Keyser, J. +3 more

The overall multi-layer structure of the magnetic field profile observed by Ulysses across a broad solar wind tangential discontinuity can be reproduced fairly well by means of a kinetic model. Such a simulation provides complementary information about the velocity distribution functions, which are not always available from the plasma experiment d…

Time-resolved Optical Spectroscopy of the Cataclysmic Variable PG 0859+415

Szkody, Paula; Hoard, D. W.

We present time-resolved, high-resolution (2 Å) spectra of the nova-like cataclysmic variable (CV) PG 0859+415. The average optical spectrum of this star displays a continuum slope that is steeper than expected for a steady state accretion disk this is attributed to the presence of a hot spot with T ∼ 12,000 K at the impact site of the accretion s…

A 21 Centimeter Absorber Identified with a Spiral Galaxy: Hubble Space Telescope Faint Object Spectrograph and Wide-Field Camera Observations of 3CR 196

Cohen, Ross D.; Junkkarinen, Vesa T.; Beaver, E. A. +3 more

We present imaging and spectroscopy of the quasar 3CR 196 (z_e = 0.871), which has 21 cm and optical absorption at z_a = 0.437.

We observed the region of Lyα absorption in 3CR 196 at z_a = 0.437 with the Faint Object Spectrograph on the Hubble Space Telescope. This region of the spectrum is complicated because of…

An Ultraviolet-Excess Optical Candidate for the Luminous Globular Cluster X-Ray Source in NGC 1851

Anderson, Scott F.; Margon, Bruce; Deutsch, Eric W. +1 more

The intense, bursting X-ray source in the globular cluster NGC 1851 was one of the first cluster sources discovered, but has remained optically unidentified for 25 years. We report here on results from Hubble Space Telescope WFPC2 multicolor images in NGC 1851. Our high spatial resolution images resolve ~200 objects in the 3" radius Einstein X-ray…

Spectroscopy and Direct Imaging of the Planetary Nebula IC 4593.

Olguín, L.; Bohigas, J.

Spectroscopy of the planetary nebula IC 4593 leads to helium, oxygen, carbon, sulfur and argon abundances which are typical of non-type I planetaries. Nitrogen abundance is normal when UV data is used. Neon might be underabundant by a factor of 2. Images in various emission lines show that the nebula is composed of two internal structures dominate…

Octupole model of Jupiter's magnetic field from Ulysses observations

Connerney, J. E. P.; Acuña, M. H.; Ness, N. F.

A spherical harmonic model of the planetary magnetic field of Jupiter is obtained from the Ulysses encounter observations. The magnetic field in the Jovian magnetosphere is represented using a degree and order 3 spherical harmonic for the planetary (``internal'') field, and an explicit model of the magnetodisc for the field (``external'') due to d…

Type III radio bursts observed by ULYSSES pole to pole, and simultaneously by wind.

Robinson, P. A.; Bougeret, J. -L.; Hoang, S. +2 more

We consider 555 type III bursts observed by Ulysses and/or Wind while Ulysses traversed a large range of longitude and latitude. We find: 1) The percentage of bursts seen by both spacecraft was 59.5%. It was higher, about 80%, when Ulysses was to the south and east of the Sun as seen from Wind. It decreased to about 50% when Ulysses was near the e…

Propagation of Solar Cosmic Rays: Diffusion versus Focused Diffusion

Vainio, R.; Torsti, J.; Kocharov, L. G. +1 more

This paper is designed to bring to the attention the fact that the effect of focusing of solar energetic particles is always essential as compared with scattering, no matter how small the value of the mean free path may be. That is why, an ordinary (`focusing-free') diffusion approach can not be applied to the solar cosmic ray transport. In the ca…