Search Publications
Spin modulated X-ray emission from intermediate polars.
Watson, M. G.; Norton, A. J.
This paper describes a comparative study of all the intermediate polars observed by Exosat. The X-ray pulse profiles of each source are presented, and it is shown that, in all cases, the modulation can be described in terms of an increasing depth with decreasing energy. By considering the pulse phase-resolved spectra, it is shown that the modulati…
Coronal Activity in F-, G-, and K-Type Stars. III. The Coronal Differential Emission Measure Distribution of Capella, sigma 2 Coronae Borealis, and Procyon
Mewe, R.; Schrijver, C. J.; Lemen, J. R. +1 more
EXOSAT soft X-ray spectra of three binary systems of cool stars are analyzed: Capella (G6 III + F9 III), Sigma-squared CrB (F8 V + G1 V), and Procyon (F5 IV-V + DF). The EXOSAT transmission grating spectrometer permits the study of individual spectral lines and line complexes between 10 and 200 A with approximately 3 A resolution. First it is demo…
Variable X-ray absorption in NGC 4151.
Warwick, R. S.; Yaqoob, T.; Pounds, K. A.
The Seyfert galaxy NGC 4151 was monitored over 20 times by EXOSAT in the period 1983 July-1986 March. The very soft spectral component detected by the EXOSAT low-energy telescope, which may be thermal emission from the narrow-line region of NGC 4151, remained constant over the observing period. In contrast, the medium-energy X-ray continuum emanat…
The X-ray ephemeris of Cygnus X-3.
van der Klis, M.; Bonnet-Bidaud, J. M.
A set of 17 measurements of the arrival time of the 4.8-hr period of the X-ray binary Cygnus X-3 over an interval of 2.3 yr are derived from Exosat data. These measurements are combined with previous data to study the period of Cygnus X-3 for the period 1970-1985. A cubic ephemeris with a 99.9 percent confidence fit to the data is presented with a…
The Discovery of 0.2 HZ Quasi-periodic Oscillations in the X-Ray Flux of the Transient 42 Second Pulsar EXO 2030+374
Stella, L.; Parmar, A. N.; Angelini, L.
The discovery of about 0.2 Hz quasi-periodic oscillations (QPOs) in the 1-15 keV X-ray flux of the transient 42 s pulsar EXO 2030 + 375 is reported. The detection of QPOs in the power spectra of this pulsar was made possible by the application of a newly developed technique to decouple the power spectrum peaks. QPOs were detected during an outburs…
Spectral characteristics of low-frequency plasma turbulence upstream of comet P/Halley
Coates, A. J.; Glassmeier, K. -H.; Neubauer, F. M. +4 more
Spectral characteristics of low-frequency plasma turbulence in a cometary environment have been determined using cross-spectral analyses of magnetic field and plasma measurements made on board the Giotto spacecraft upstream of comet P/Halley. Two upstream regions have been identified, where the mean solar wind magnetic field was approximately para…
An EXOSAT X-Ray Observation of One Orbital Cycle of 4U 1700-37/HD 153919
Haberl, F.; White, N. E.; Kallman, T. R.
Exosat observations of close to one complete binary cycle of 4U 1700-37/HD 153919 are presented, and X-ray absorption variations are determined as a function of orbital phase in order to study the properties of the stellar wind of the companion HD 153919. The decrease noted in absorption between eclipse egress and phase 0.5 may be due to X-rays fr…
The Kinematics of Milky Way Halo Gas. I. Observations of Low-Ionization Species
Danly, Laura
Ultraviolet interstellar line day observed with the IUE toward 70 halo stars and four extragalactic sight lines are analyzed in a study of the large-scale kinematic properties of the Milky Way halo gas. The motions of the low-ionization gas is focused on. Large systematic velocities are found, and a pronounced asymmetry in the absorption character…
The nucleus of comet Halley: Surface structure, mean density, gas and dust production
Rickman, H.
The relation between the mass of a cometary nucleus, its gas production curve, the mean outflow velocity, and the nongravitational delay of the comet is discussed, emphasizing the properties of gaseous outflow from comet Halley. The importance of knowledge about the rotational state of the nucleus is stressed, and it is argued that the likely wobb…
X-Ray Observations of the Starburst Galaxy M82
Pietsch, W.; Schaaf, R.; Kronberg, P. P. +2 more
We report here on long (~ 10^5^ s) X-ray observations of the starburst galaxy M82 with the European X-ray satellite EXOSAT. The observations with the low-energy imaging instrument confirm that there is extended X-ray emission from above and below the disk, with an overall extent perpendicular to the disk of almost 6' corresponding to 6 kpc. We pre…