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Comparison of picked-up protons and water group ions upstream of comet Halley's bow shock
Coates, A. J.; Neubauer, F. M.; Neugebauer, M.
Data are presented on the properties of picked-up cometary protons and water group (WG) ions observed upstream of the bow shock of comet Halley by the ion mass spectrometer and Johnstone plasma analyzer experiments on the Giotto spacecraft. The number of WG ions exceeded the number of cometary protons at cometocentric distances r<1.3×106
The Evolution of Magnetic Activity on V711 Tauri and Evidence for a Significant Facular Contribution
Guinan, E. F.; Dorren, J. D.
The nature of the long-term evolution of magnetic activity in the RS CVn binary V711 Tauri is investigated using the complete set of available archival IUE SWP low-dispersion spectra of V711 Tau for the period covering August 1978 - December 1984. An analysis of the spectra confirmed the pattern of a long-term smooth variation of chromospheric and…
Giotto magnetic field observations at the outbound quasi-parallel bow shock of comet Halley.
Coates, A. J.; Neubauer, F. M.; Glassmeier, K. H. +4 more
The investigation of the outbound bow shock of comet Halley using Giotto magnetometer data leads to the following results: the shock is characterized by strong magnetic turbulence associated with an increasing background magnetic field and a change in direction by 60° as one goes inward. The thickness of the quasi-parallel shock was 120000 km. The…
The absolute magnitudes of RR Lyrae stars - III. DH Peg.
Jameson, R. F.; Fernley, J. A.; Skillen, I. +1 more
UV optical and IR photometry of the RRc Lyrae star DH Peg is presented. Using this photometry plus previously published data the IR Flux Method of Blackwell & Shallis (1977) is applied to estimate effective temperatures and angular diameters at all phases of the pulsation cycle. The angular diameters are then matched with the integrated radial…
Optical Variability of Extragalactic Objects Used to Tie the HIPPARCOS Reference Frame to an Extragalactic System Using Hubble Space Telescope Observations
Bozyan, Elizabeth P.; Hemenway, Paul D.; Argue, A. Noel
Observations of a set of 89 extragalactic objects (EGOs) will be made with the Hubble Space Telescope Fine Guidance Sensors and Planetary Camera in order to link the HIPPARCOS Instrumental System to an extragalactic coordinate system. Most of the sources chosen for observation contain compact radio sources and stellarlike nuclei; 65% are optical v…
The X-ray orbital lightcurve of TY Pyx : a 3.2-day eclipsing RS CVn system.
Parmar, A. N.; White, N. E.; Culhane, J. L. +1 more
An Exosat observation of one orbital cycle of the eclipsing 3.2-d RS CVn system TY Pyx is reported. This system contains two almost identical GV stars, which is unusual because most RS CVns contain F or G main-sequence star and a K subgiant. The X-ray light curves of the primary and secondary eclipses are different above and below 1 keV. At lower …
The UV variability of BF Cygni.
Gonzalez-Riestra, R.; Cassatella, A.; Fernandez-Castro, T.
BF Cygni is one of the symbiotic systems in which orbital effects are better seen. The UV continuum and emission lines undergo large variations, in good agreement with the predictions of optical photometry. The strong changes in the shape of the ultraviolet continuum suggest the existence of a strongly wavelength dependent opacity. At least at som…
Ultraviolet Colors as Age Indicators for LMC Clusters
Freeman, K. C.; Meurer, Gerhardt R.; Cacciari, C.
Empirical correlations are found between log ages (logτ) intrinsic ultraviolet colors C(18 - 31)_0_ and C(25 - 31)_0_ for 27 LMC clusters, where log τ is on the uniform age scale of Elson correlations as age indicators for LMC clusters and other stellar populations are discussed. The results are partially based on a new calibration of log τ vs the…
IUE and Einstein Survey of Late-Type Giant and Supergiant Stars and the Dividing Line
Maggio, A.; Vaiana, G. S.; Haisch, Bernhard M. +2 more
Results are presented on an IUE UV survey of 255 late-type G, K, and M stars, complementing the Maggio et al. (1990) Einstein X-ray survey of 380 late-type stars. The large data sample of X-ray and UV detections make it possible to examine the activity relationship between the X-ray and the UV emissions. The results confirm previous finding of a t…
Lyman-alpha and MG II H and K fluxes in a sample of dwarf M stars.
Doyle, J. G.; Byrne, P. B.; Panagi, P.
Ly-alpha and Mg II fluxes are given for a group of M dwarfs. The Ly-alpha and Mg II lines were extracted from low resolution spectra taken with the IUE satellite. The Ly-alpha line is shown to be an important source of radiative losses in dMe chromospheres, being at least a factor of two more important than Mg II. Overall it contributes approximat…