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The Heliosphere and the Ulysses Mission
Balogh, A.
The interplanetary medium consists primarily of the supersonic solar wind, carrying the frozen-in magnetic field extending from the solar corona. The properties of this medium are controlled by the state of the corona and by dynamic processes occurring in the medium itself. As a result, there are significant variations in those properties as a fun…
The radial brightness dependence in the dust coma of comet P/Grigg-Skjellerup.
Fulle, M.; Mennella, V.; Colangeli, L. +2 more
In a previous paper (Fulle et al. 1993a) we have obtained a three-dimensional coma model of the short period comet P/Grigg-Skjellerup, by fitting ground-based images taken in coincidence with the fly-by of the GIOTTO spacecraft (GEM mission). Concerning the cometary dust environment, we confirmed the excess of large grains measured by the in-situ …
The helium-to-hydrogen ratio of the UV-bright star Barnard 29 of Messier 13.
Adelman, S. J.; Sweigart, A. V.; Aikman, G. C. L. +2 more
Barnard 29 is the most luminous UV-bright star of the globular cluster Messier 13. Comparison of its reddening corrected optical region spectrophotometry and IUE low dispersion fluxes and its H-gamma profile with the predictions of metal-poor model atmospheres having the metallicity of M 13 indicated Teff = 20250 K, log g = 3.15. Observ…
Hot stars near the position of X0512-401 in the globular cluster NGC 1851.
Bonnet-Bidaud, J. M.; Koch-Miramond, L.; Auriere, M.
We have conducted an investigation of the error box of the X-ray source in NGC 1851 in the optical (ESO, La Silla) and ultraviolet (IUE) ranges. The central field of NGC 1851 was observed in UBV CCD photometry. Two IUE observations, with different slit orientations were used (one from archives, one obtained for this study). The optical photometry …
Particle acceleration by an interplanetary shock-pair seen at ULYSSES at 3.15 AU.
Tappin, S. J.; Lanzerotti, L. J.; Roelof, E. C.
Observations from the HI-SCALE instrument on Ulysses of the ions and electrons associated with an interplanetary shock-pair at about 3.15 AU are presented. An empirical model is used to derive the evolution of the particle distribution in the solar wind frame. The forward shock is shown to be the primary source of ion acceleration, while the weake…
Analytic Lyman-Alpha Wing Diagnostics and the Chromospheric Excitation Balance in Cool Dwarfs
Gayley, K. G.
I show that the Lyman alpha wings of cool dwarfs can be understood in terms of a very simple model, based on a simplified representation of the chromospheric hydrogen excitation balance and approximate analytic wing diagnostics in partial redistribution. Much of the complexity of the radiation transfer in the partially coherent and steeply tempera…
Ultraviolet Photometry of Nova Cygni 1992 Obtained with the High Speed Photometer
Gallagher, J. S.; Nelson, M. J.; Percival, J. W. +6 more
In this Letter we present the first high-speed ultraviolet photometry of an active, classical nova, Nova Cygni 1992. The 45 minute observation shows significant evidence for power at frequencies that correspond to periods of about 565 and 900 s. Each of these periods has an amplitude of about 3 mmag. Since this data set is short, we cannot establi…
Optical Signatures of High-Redshift Galaxy Clusters
Charlot, Stephane; Evrard, August E.
We combine an N-body and gasdynamic simulation of structure formation with an updated population synthesis code to explore the expected optical characteristics of a high-redshift cluster of galaxies. We examine a poor (2 keV) cluster formed in a biased, cold dark matter cosmology and employ simple, but plausible, threshold criteria to convert gas …
Multiwavelength observations of RV Tauri stars II. U Monocerotis
Evans, A.; Marang, F.; Shenton, M. +3 more
We present ultraviolet spectroscopy, and optical and infrared photometry, of the RV variable U Mon. The MgII emission in this object seems to be chromospheric, with small variations in profile accompanying pulsational variations. The wavelengths of narrow absorption features associated with the MgII emission are essentially constant in time, and s…
CCD Photometry Results on Some Hipparcos Stars
Walker, Gary
This paper summarizes the status of the AAVSO CCD Photometry Program through May of 1994. The findings of the CCD questionnaire covering such topics as types of equipment, software, filters, and cameras are discussed. The first six months' observations are discussed and compared to visual observations, and the AAVSO CCD Photometry Program is evalu…