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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…
From Interstellar Dust to Comets: A Unification of Observational Constraints
Greenberg, J. Mayo; Hage, J. I.
The interstellar dust model of comets is numerically worked out to satisfy simultaneously several basic constraints provided by observations of Comet Halley, and to derive the porosity of coma dust. The observational constraints are (1) the strengths of the 3.4 and 9.7 micron emission bands, (2) the shape of the 9.7 micron band, (3) the amount of …
Variability in the noise properties of Cygnus X-1.
Belloni, T.; Hasinger, G.
The aperiodic variability in the X-ray emission of Cyg X-1 is examined from 13 Exosat observations covering the period July 1983 - October 1985, by means of broad band 0.001-100 H3 power spectra. The total rms fractional variations in the range 0.016-14 Hz is between 28 and 38 percent. The power distribution is flat below a characteristic break fr…
Observations of Cygnus X-2 with IUE : ultraviolet results from a multiwavelength campaign.
Raymond, J. C.; Hasinger, G.; Verbunt, F. +3 more
IUE observations of Cyg X-2 obtained during June and October 1988 are reported and analyzed, with reference to data from simultaneous X-ray and radio observations and the predictions of theoretical models. The results are presented in extensive tables and graphs and characterized in detail. The UV flux is shown to increase monotonically as the X-r…
An atlas of aperiodic variability in HMXB.
Belloni, T.; Hasinger, G.
From EXOSAT archive data of 14 X-ray binaries (12 high mass X-ray binaries and 2 low mass X-ray binaries) broad band power spectra and color- color diagrams are produced. The aperiodic (noise) variability of the sources is studied. All the X-ray pulsars present in the sample show strong noise components in the emission, with a fractional variabili…
X-ray emission from solar neighbourhood flare stars : a comprehensivesurvey of EXOSAT results.
Tagliaferri, G.; Stella, L.; Pallavicini, R.
Exosat Observatory observations of flare stars pertaining to 25 separate sources are examined. The Exosat instrumentation is described, and a data sample is presented. Quiescent and flaring emissions from UV Ceti-type flare stars as observed with a low-energy experiment on Exosat are discussed, and the results of the timing analysis of the low-ene…
A Study of BL Lacertae--Type Objects with EXOSAT. I. Flux Correlations, Luminosity, Variability, and Spectral Variability
Maccagni, D.; Giommi, P.; Garilli, B. +2 more
Results are presented from a uniform and systematic analysis of more than 200 X-ray observations of 36 BL Lacertae objects obtained from the EXOSAT archive. All but two objects were detected at least once. Strong luminosity variability, which reached a factor of 30 in one case, was a common property of these objects. Variability was usually more p…