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Radial and azimuthal components of the heliospheric magnetic field: ulysses observations

Forsyth, R.; Balogh, A.; Burton, M. E. +2 more

Two invariants associated with the Parker model of the solar wind involve the radial, B_R, and azimuthal, B_T, components of the heliospheric magnetic field. These invariants have been investigated using Ulysses data obtained at high latitudes in both the north and south solar hemispheres. The magnetic flux invariant, r^2B_R, is essentially indepe…

An Anomalous Ultraviolet Extension in NGC 6251

Crane, P.; Vernet, J.

Deep U-band Faint Object Camera (FOC) images of the nuclear region of NGC 6251 have revealed a region of extended emission that is most probably radiation scattered from a continuum source in the nucleus. This radiation lies interior to a dust ring, is nearly perpendicular to the radio jet axis, and is seen primarily in the FOC U and B filters. Th…

The relationship between UV and X-ray active region structures

Matthews, S. A.; Harra-Murnion, L. K.

Yohkoh and the Coronal Diagnostic Spectrometer (CDS) on the Solar and Heliospheric Observatory (SOHO) jointly observed two brightenings in active region NOAA 7981 on 6 August 1996. Combining the UV data from CDS with information from the high time resolution coronal images obtained with the Soft X-ray Telescope (SXT) on Yohkoh, provides us with im…

The Star-Formation History in the Vicinity of NGC 1866 in the Large Magellanic Cloud

Watson, A. M.; Holtzman, J. A.; Stapelfeldt, K. R. +15 more

To expand on the recent single WFPC2 field obtained in the vicinity of this cluster, we have measured the luminosity function in a one-third by one-half degree field in the LMC with the 40 inch telescope at Siding Spring Observator. Combining our results with recent 4-meter and WFPC2 observations, we examine the constraints on the star formation h…

The Axis Ratio Distribution of Local and Distant Galaxies

Windhorst, Rogier A.; Burstein, David; Odewahn, Stephen C.

Surface photometry from 16 HST/WFPC2 fields in the I₈₁₄-band filter is used to derive the distribution of apparent axis ratios for galaxies in progressively fainter magnitude intervals for I₈₁₄≤25. We assess the systematic and accidental errors in ellipticity measurements as a function of image resolution and signal-to-noise …

The iron abundance in helium star HD 144941.

Jeffery, C. S.; Harrison, P. M.

The iron abundance in the helium star HD 144941 has been measured from ultraviolet #1iii lines. It is 1.9+/-0.2dex below solar and confirms the low metallicity (Z=0.0003) previously determined from measurements of CNO and other light elements. The result is important because the low CNO metallicity must be reflected in the iron-group elements in o…

Atomic Physics with the Goddard High Resolution Spectrograph on the Hubble Space Telescope. III. Oscillator Strengths for Neutral Carbon

Federman, S. R.; Cardelli, Jason A.; Zsargo, J.

High quality spectra of interstellar absorption from C I toward β¹ Sco, ρ Oph A, and χ Oph were obtained with the Goddard High Resolution Spectrograph on HST. Many weak lines were detected within the observed wavelength intervals: 1150-1200 Å for β¹ Sco and 1250-1290 Å for ρ Oph A and χ Oph. Curve-of-growth analyses were perf…

Lyα Absorption-Line Systems in the Gravitational Lens Q0957+5611

Bruhweiler, F. C.; Michalitsianos, A. G.; Kazanas, D. +6 more

Far-ultraviolet spectra of the gravitational lens components Q0957+561A and B were obtained with the Hubble Space Telescope Faint Object Spectrograph (HST FOS). Two previously known absorption-line systems were detected at redshifts z_damped = 1.3911 and z_Lyα = 1.1249. Their prominent absorption features are superposed on inte…

Measurement of the ^12C/^13C ratio in planetary nebulae

Walsh, J. R.; Clegg, R. E. S.; Storey, P. J. +1 more

The ^12C/^13C isotopic ratio in the ionized gas in three planetary nebulae has been measured using a new method based on transitions caused by hyperfine effects. The C III] multiplet near 1908A has an F=1/2-1/2 transition at 1909.6A that is completely forbidden in ^12C, but allowed as a result of the non-zero nuclear spin of ^13C. The transition p…

The Cluster Mission: ESA`S Spacefleet to the Magnetosphere

Credland, J.; Mecke, G.; Ellwood, J.