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The stellar content of a spiral arm of NGC 4321
Dolphin, Andrew E.; Hodge, Paul W.; Wyder, Ted K.
The effects of the passage of a spiral arm through the disc of the giant Virgo Sc galaxy NGC 4321 are investigated with Hubble Space Telescope WFPC2 images in two colours. Concentrating on a portion of the southern spiral arm of NGC 4321, we have applied a new program to solve for the star formation histories in the arm and interarm regions separa…
On an ultraviolet spectral atlas of alpha2 CVn
Wahlgren, G. M.
We describe the ultraviolet spectra of the Ap star alpha 2 CVn that have been acquired with the Hubble Space Telescope and the nature of the optical region analyses for its rotational velocity and elemental abundances that have been undertaken in support of the ultraviolet data.
The new astrometry
Kovalevsky, J.
First, the main objectives of astrometry are presented and the most important features or phenomena that intervene in the measurement of positions of celestial objects are shortly described. Then, the two classical astrometric techniques that are still very much used, especially since the invention of CCDs, transit instrument and astrophotography,…
Low energy anomalous ions at northern heliolatitudes
Lanzerotti, L. J.; Maclennan, C. G.
Measurements of the anomalous component of nitrogen, oxygen, and neon ions (∼0.5-8 MeV/nucl.) at northern heliolatitudes by the HI-SCALE instrument on the Ulysses spacecraft show that the energy spectra of these ions are essentially flat from the highest heliolatitudes (80° N) to near the ecliptic plane. For energies from 1-8 MeV/nucl., the northe…
Infrared Properties of a Large Ring Around the LBV G79.29+0.46
Landecker, T. L.; Heske, A.; Wendker, H. J. +2 more
G79.29+0.46 seems to be an unique object. Discovered as a nearly perfect ring in the radio continuum all subsequent observations are consistent with the interpretation that it is a large ring nebula (4‧) around an heavily reddened LBV. Our ISOPHOT and LWS observations on board of ISO show that an infrared ring coincides with the radio ring. Line e…
The Cassini-Huygens SSP refractometer : ref
Geake, J. E.; Mill, C. S.
The refractometer (REF) in the Huygens probe Surface Science Package (SSP) is a linear critical-angle refractometer ; it covers the refractive index range 1.2500-1.4500 with a discrimination of 0.0005, giving an accuracy of about 0.5% in the relative abundance of methane and ethane in the expected mixture on the possibly liquid surface of Titan. L…
On the diamagnetic effect associated with the ion pile-up region in the coma of comet Halley
Neubauer, F. M.; Israelevich, P. L.; Ershkovich, A. I.
The ion pile-up region in the comet Halley ionosphere observed on the inbound leg of the Giotto trajectory is accompanied by a decrease of the magnetic field strength. This magnetic field dip is explained by means of a diamagnetic effect of the plasma density increase in the pile-up region. Maximum of the plasma pressure seems to coincide with the…
Accuracy of Plasma Moment Derivatives
Vogt, Joachim; Paschmann, Götz
Solar Wind
Marsch, Eckart
A concise tutorial review is given of solar wind observations and theory with emphasis on the more recent findings from the Ulysses and SOHO missions, in particular about the plasma state and structure of the polar coronal holes, and on theoretical efforts to model the coronal hole flows and the fast solar wind emanating therefrom. The structure o…
Hubble Space Telescope Spectra of 3C 279: A Lyman Limit System at Low Redshift
Stocke, John T.; Blades, J. Chris; Penton, Steve +2 more
We present Hubble Space Telescope (HST) Faint Object Spectrograph spectra of the blazar 3C 279 obtained during two recent optical outbursts of this source, maximizing the sensitivity to weak foreground absorption systems at far-UV wavelengths for this sight line. Eighteen absorption systems were detected above an observed 3 sigma limiting equivale…