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Hipparcos: First results of the photometric processing
Mignard, F.; Grenon, M.; Falin, J. L. +1 more
The analysis of the photon counts collected by the ESA HIPPARCOS satellite allows to determine for each program star a magnitude in the H-filter. We present the general principles of the data reduction restricted to the photometry. It is shown that photometric recognition of close binary stars, down to 100 arcsec separation is an attainable goal, …
Strong Absorption Lines in the Spectrum of Supernova 1987A in the First Months after the Explosion - Variations of Lines of Heavy Elements
Lyubimkov, L. S.
IUE spectral analysis of the Be star HD 184279.
Hirata, R.; Dawanas, D. N.
Luminosity of large amplitude variable stars: Comparison between ground-based predictions and observations by the Hipparcos satellite
Barthes, D.; Mennessier, M. O.; Davies, P.
Since November 1989, the HIPPARCOS satellite has been observing stars in order to fulfil its mission goals. The complete data processing of these observations will take many years to perform. A small group of stars, namely the large amplitude variables, must be processed much closer to real-time so that the luminosity ephemeris can be updated wher…
X-ray astronomy in its thirtieth year.
Pounds, K. A.
An overview is given of current activities and future prospects in the X-ray astronomy field with attention given to the British involvement in the Ginga, Rosat, and Exosat projects. The large array of proportional counter detectors for the Ginga astronomy satellite is described in detail with respect to studying time variability. The Rosat X-ray-…
Cometary ion distributions near the pickup energy outside comet Halley's bow shock
Coates, A. J.; Neugebauer, M.; Gombosi, T. I. +2 more
This paper compares calculated and measured energy spectra of implanted H+ and O+ ions on the assumption that the pick-up geometry is quasi-parallel and about 1% of the waves generated by the cometary pickup process propagates backward (towards the comet). The model provides a good description of the implanted O+ a…
Dust-acoustic waves in dusty plasmas
Yu, M. Y.; Shukla, P. K.; Rao, N. N.
New acoustic waves originating from a balance of dust particle inertia and plasma pressure are investigated. It is shown that these waves can propagate linearly as a normal mode in a dusty plasma, and non-linearly as supersonic solitons of either positive or negative electrostatic potential.
Terminal Velocities for a Large Sample of O Stars, B Supergiants, and Wolf-Rayet Stars
Barlow, M. J.; Howarth, Ian D.; Prinja, Raman K.
It is argued that easily measured, reliable estimates of terminal velocities for early-type stars are provided by the central velocity asymptotically approached by narrow absorption features and by the violet limit of zero residual intensity in saturated P Cygni profiles. These estimators are used to determine terminal velocities, v(infinity), for…
An Analysis of the Shapes of Ultraviolet Extinction Curves. III. an Atlas of Ultraviolet Extinction Curves
Fitzpatrick, Edward L.; Massa, Derck
The basic data needed to produce UV extinction curves for a sample of 78 stars, including spectral types, visual photometry, parameters used to produce fits to the UV extinction curves, distances to the program stars, and line-of-sight H I column densities, are presented. The observational and numerical techniques used to obtain the results are di…
Multi-frequency variations of the Wolf-rayet system HD 193793 - I. Infrared, X-ray and radio observations.
van der Woerd, H.; van der Hucht, K. A.; Pollock, A. M. T. +3 more
Observations made of the Wolf-Rayet system HD 193793 over the 1979-1989 period in the radio, X-ray, and IR regions reveal great variations in all three regimes. The most complete coverage obtained was in the IR; attention is given to an IR outburst in 1985 during which the IR flux increased by as much as an order of magnitude over the course of se…