Search Publications
Trajectories of charged dust grains in the cometary environment
Horanyi, M.; Mendis, D. A.
Using a simple model of the particles and fields environment of a comet, the trajectories of the smallest (micron- and submicron-sized) dust grains that are expected to be released from a cometary nucleus are calculated. It is shown that electromagnetic forces play a crucial role in the dynamics of these particles. The present calculations indicat…
The gaseous component of the disk around beta Pictoris.
Ferlet, R.; Vidal-Madjar, A.; Gry, C. +2 more
Optical spectra of alpha Lyr, alpha PsA, and beta Pic have been obtained at a velocity resolution of 3 km/s. No circumstellar absorption lines of Ca II or Na I are detected toward alpha Lyr or alpha PsA at sensitive limits. In the favorable case of beta Pic, where the circumstellar disk imaged by Smith and Terrile (1984) is seen nearly edge-on, a …
Winds in central stars of planetary nebulae.
Perinotto, M.; Cerruti-Sola, M.
The physical properties of stellar winds have been studied using the low-resolution IUE spectra for 60 central stars in planetary nebulae. Approximately half of the 42 stars with a measurable stellar continuum displayed P Cygni profiles in UV absorption lines. The appearance of wind was correlated with stellar temperature and radius. Central stars…
The evolution of spiral galaxies and uncertainties in interpreting galaxy counts.
Ellis, R. S.; King, C. R.
Evolutionary models are discussed with respect to the interpretation of faint galaxy counts. The K-corrections are reviewed with available UV data, and the necessary assumptions and model input parameters. In particular the possibility that the bulges of spiral galaxies have evolved in a form similar to that expected for elliptical galaxies is exp…
The old nova GK Per : discovery of the X-ray pulse period.
King, A. R.; Watson, M. G.; Osborne, J.
EXOSAT observations of GK Per during an optical outburst are reported. The hard X-ray emission (greater than 2 keV) shows a strong coherent modulation at a period of 351 s, identifying GK Per as the latest member of the 'intermediate polar' subclass of magnetic cataclysmic variables. The X-ray pulse profile has a quasi-sinusoidal shape with mean a…
The Structure of Low-Mass X-Ray Binaries
White, N. E.; Mason, K. O.
The present knowledge of the structure of low-mass X-ray binary systems is reviewed. We examine the orbital period distribution of these sources and discuss how the orbital periods are measured. There is substantial observational evidence that the accretion disks in low-mass X-ray binaries are thick and structured. In a number of highly inclined s…
The discovery of 4.4 second X-ray pulsations from the rapidly variable X-ray transient V 0332+53.
Stella, L.; Parmar, A. N.; White, N. E. +3 more
Using the EXOSAT Observatory, three outbursts from the transient X-ray source V0332 + 53 have been observed between November 1983 and January 1984. It is found that in addition to the rapid Cyg X-1-like variability previously reported by Tanaka et al. (1983), this source also displays stable pulsations with a period of 4.4 s. Doppler variations in…
EXOSAT observations of broad iron K line emission from Scorpius X-1.
White, N. E.; Taylor, B. G.; Peacock, A.
Using the Exosat Gas Scintillation Proportional Counter a broad iron K emission line is found to be present in the X-ray spectrum of Sco X-1. The line full width half-maximum (FWHM) is 0.7 keV, independent of the source intensity state. During flaring intervals the line intensity remains constant such that the equivalent width, decreases from 50 e…
The apsidal motion of the eccentric eclipsing binary DI Herculis - an apparent discrepancy with general relativity.
Guinan, E. F.; Maloney, F. P.
DI Her is an important system for studying relativistic apsidal motion because of the large masses and small fractional radii of its components, the large orbital eccentricity and its relatively short period, and the favorable orientation of its orbital plane to our line of sight producing deep eclipses. In addition, the long history of eclipse ti…
An X-ray study of AM Herculis. I. Discovery of a new mode of soft X-ray emission.
Stella, L.; Heise, J.; King, A. R. +4 more
The discovery of a new mode of soft X-ray emission of the magnetic cataclysmic variable AM Her is reported. AM Her has been observed in June, August and September 1983 with EXOSAT in both hard (1-30 keV) and soft (40-120 A) X-rays. Hard X-rays were seen to be partially eclipsed and periodic with the white dwarf rotation period. The eclipse phases …