Search Publications
Detecting X-ray QPOs in active galaxies
Vaughan, Simon; Uttley, Philip
Since EXOSAT produced the first good quality X-ray light curves of Seyfert galaxies there have been several claims of quasi-periodic oscillations (QPOs). None of these have withstood repeated analyses and observations. We review some problems concerning the detection of QPOs.
The discovery of 8.7 S pulsations from the ultrasoft X-ray source 4U0142+61
Mereghetti, S.; Stella, L.; Israel, G. L.
We discovered a periodicity at ~8.7 s from the X-ray sources 4U0142+61, previously considered a possible black hole candidate on the basis of its ultrasoft spectrum. The pulsations are visible only in the 1-4 keV energy range, during an observation obtained with the EXOSAT satellite in August 1984. In the same data, periodic oscillations at 25 min…
The highly ionised absorbing material in MR2251-178
Mineo, T.; Stewart, G. C.
Ginga observations have suggested the presence of iron absorption edges at energies appropriate for highly ionised material in the X-ray spectra of a significant number of active galactic nuclei. Here, we present a detailed self-consistent analysis of a series of Ginga and EXOSAT observations of MR2251-178, the original prototype of this warm-abso…
Einstein and EXOSAT observations of Geminga revisited
Bignami, G. F.; Mereghetti, S.; Caraveo, P.
We have re-analyzed the archive Einstein IPC and EXOSAT CMA x-ray data of Geminga, in the light of the recent discoveries on this source. The results of a search for the 237 msec periodicity are consistent with a pulsed fraction decreasing with x-ray energy. We have combined the EXOSAT CMA and the Einstein data in order to limit the spectral param…
Multiwavelength astronomy using ESIS
Giommi, P.; Ansari, S. G.
We present results on multi-frequency astronomy obtained using the European Space Information System, ESIS. ESIS is an ESA service designed to access, manipulate and combine archival data from a number of remote archives in the fields of Astronomy and Space Physics. The examples presented here include plots of radio-to-X-ray energy distribution of…
Two-component continuum spectrum X-ray pulsar EXO2030+375
Li, T. P.; Cheng, L. X.; Sun, X. J. +1 more
We report the detection of a soft X-ray component in the spectrum of the transient X-ray pulsar EXO2030+375 at a high state in 1985. The spectrum of the soft X-ray component could be fitted by a blackbody with a temperature kT ∼1.1 keV and a radius of the emission areaR ∼ 3.6 - 6.1 km (assuming 5 kpc distance).
EXOSAT observations of the iron line in CEN X-3
Fabian, A. C.; Tennant, A. F.; Takalo, L. O.
Properties of the iron line in Cen X-3 have been studied, using the gas scintillation proportional counter onboard EXOSAT. The iron line energy is seen to be constant (kT = 6.59 +/- 0.06 keV) over orbital and pulse periods. On the other hand the iron line intensity is seen to vary with both periods. The pulse period variations are sinusoidal, but …
Astronomy with EXOSAT
White, N. E.
The European Space Agency's X-ray observatory EXOSAT was operational from May 1983 to April 1986 and in that time made 1780 observations of a wide variety of objects including active galactic nuclei, stellar coronae, cataclysmic variables, white dwarfs, X-ray binaries, clusters of galaxies and supernova remnants. The 90hr high earth orbit allowed …
Time variability of stellar coronal sources observed by EXOSAT
Schmitt, J. H. M. M.; Pallavicini, R.
We present an overview of time variability in stellar coronal sources as observed with the EXOSAT satellite. We focus on M dwarf flare stars and we discuss both quiescent and flaring emission. We also outline recent developments in the modelling of stellar flares.
Temperatures of coronae of cool stars, derived from EXOSAT observations
Mewe, R.; Schrijver, C. J.; Lemen, J. R.
We observed the late-type stars Capella, σ2 CrB, λ And, AD Leo, GL494, GL569 and Procyon with different combinations of three instruments aboard EXOSAT : the low-energy channel multiplier array (LE), the medium-energy proportional counters (ME), and the transmission grating spectrometer (TGS). We derive crude temperature information on …