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Variability of GX 3+1 observed with EXOSAT.
Frontera, F.; Stella, L.; Robba, N. R. +1 more
The authors report results from an observation of the X-ray source GX 3+1 carried out with the EXOSAT satellite on 1983, October 23. The source showed a strong X-ray variability in excess of the counting statistics noise. This variability increased toward low frequencies ("red noise") and was different in different energy bands, with the lower ene…
First ultraviolet observations of the transition regions of X-ray bright solar-type stars in the Pleiades
Linsky, J. L.; Caillault, J. -P.; Vilhu, O.
Nearby clusters, such as Ursa Major, the Hyades, and the Pleiades, have been extensively studied in the X-ray regime. The first two clusters have also been studied with the IUE. However, the younger, fainter Pleiades cluster, which contains the youngest, and presumably most active, main sequence stars in the solar vicinity, had not been observed i…
X-Ray Observations of Gamma-Ray Burst Sources
Hurley, K.; Boer, Michel; Pizzichini, G. +1 more
We report on preliminary results of EXOSAT observations of three gamma-ray burst error boxes. No source was detected down to a limit of 10‑10 erg cm‑2s‑1, assuming a black-body spectrum for the burst counterpart. Results are interpreted in the framework of current theoretical models.
Highlights from the COS-B mission
Hermsen, W.
The European Space Agency's high-energy (E>50 MeV) gamma-ray observatory COS-B was operational from August 1975 to April 1982 and in that time made 65 observations of about 1 month duration and with a field-of-view of approximately 0.4 sr each. The high counting statistics achieved over the total mission allowed, for the first time, a detailed …
Gamma-ray constraints on the Galactic halo
Bloemen, J. B. G. M.
Some findings from recent COS-B analyses of the diffuse Galactic γ-ray emission are briefly summarized, with emphasis on their impact for our understanding of the Galactic cosmic-ray halo.
Gamma rays from dark clouds.
Feitzinger, J. V.; Stuewe, J. A.
The distribution of dark clouds and the COS-B X-ray observations of the local interstellar medium at intermediate galactic latitudes are compared. The dark cloud catalog of Lynds (1962) is combined with the complementary work of Feitzinger & Stuewe (1986) to obtain a uniform coverage of the medium-latitude sky. A good correlation between the e…
Two patterns of correlated X-ray timing and spectral behaviour in low-mass X-ray binaries.
van der Klis, M.; Hasinger, G.
Exosat data are used to study the power spectra of 16 LMXBs as a function of their behavior in X-ray color-color diagrams. The study confirms the existence of a class of sources with three-branched Z-shaped colour-colour diagrams characterized by a temporal behavior that is strongly dependent on the position of the source on the Z. Evidence for an…
Accretion-powered X-ray pulsars.
Nagase, Fumiaki
This paper gives an overview of X-ray pulsars powered by the accretion of matter from a companion star in a close binary system. Recent advances in studies of X-ray pulsars are reviewed, with a special focus on the results of observations by the Hakucho and Tenma satellites. Some topics revealed by the Ginga satellite in the last one-and-a-half ye…
The EXOSAT spectral survey of AGN.
Turner, T. J.; Pounds, K. A.
Results are presented from EXOSAT Observations of 48 hard X-ray selected Seyfert type active galactic nuclei (AGN). These include all 30 of the emission line AGN in the Piccinotti sample. Combining EXOSAT LE and ME data has allowed us to obtain X-ray spectra over the broad energy range 0.1 - 10 keV spectra in the ~2-10 keV range are found to be we…
The Stellar Winds of 203 Galactic O Stars: A Quantitative Ultraviolet Survey
Howarth, Ian D.; Prinja, Raman K.
Measurements of the resonance lines of C IV, N V, and Si IV in a sample of 203 O stars observed using IUE in a high-resolution mode are presented. The data are discussed using a consistent set of radius, luminosity, and mass estimates. The ratio of the maximum observed velocity and the terminal (farfield) velocity is found to average at 3.0 for 13…