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EXOSAT observations of a strong soft X-ray excess in MKN 841.
Culhane, J. L.; Fabian, A. C.; Branduardi-Raymont, G. +6 more
EXOSAT observations of the spectrum of the Seyfert 1 galaxy MKN 841 show that it is well-fitted by a power law of photon index 1.6, similar to that of other Seyferts, and a large additional soft component. The X-ray luminosity over the observed band exceeds 4×1044erg s-1. A single-temperature blackbody fit to the soft X-rays …
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…
Continuous rapid X-ray variability and spectral changes in NGC 4051.
Elvis, M.; Watson, M. G.; Lawrence, A. +1 more
The observation of rapid X-ray variability in active galaxies is of great potential interest. In Seyfert galaxies, variability on a time-scale of days seems common, but fast (minutes-hours) variability is apparently very rare. In a variability survey with the HEAO-1 A2 experiment, Tennant and Mushotzky (1983) found only one object to vary on short…
The discovery of low-level iron K line emission from CYG X-1.
White, N. E.; Barr, P.; Page, C. G.
The results of seven observations of the X-ray spectrum of Cyg X-1, made using the gas scintillation proportional counter on board the Exosat Observatory are presented. The discovery of a broad emission feature at 6.2 keV is reported with an equivalent width of typically 120 eV. The line is resolved to have an FWHM of about 1.2 keV. There is no ev…
EXOSAT soft X-ray observations of EX Hydrae.
Kahn, S. M.; Mason, K. O.; Cordova, F. A.
During a continuous 26 hour X-ray observation of the 98-min binary EX Hydrae using the CMA detector on EXOSAT, a 67-min modulation was detected with a pulse-fraction of about 30 per cent. The phase of the modulation coincides with that of the 67-min optical modulation which has a pulse-fraction of 15 per cent. The X-ray and optical pulse shapes ar…
EXOSAT MEDA observations of Cygnus X-3.
King, A. R.; Pounds, K. A.; Willingale, R.
Results of a continuous 30.6-hr X-ray observation of Cygnus X-3 with a large area detector are presented. These show the well known, roughly sinusoidal light curve at the 4.8-hr period, with a phase-dependent variability at short time-scales, and associated spectral behavior. The sinusoidal modulation is interpreted as due to electron scattering i…
Simultaneous X-ray and optical observations of the X-ray dip source X1755-338.
Parmar, A. N.; White, N. E.; Mason, K. O.
Simultaneous X-ray and optical observations have been made of the 'dipping' X-ray source X1755-338 which has a dip recurrence period of 4.4 hr. A sinusoidal modulation of amplitude 0.4 mag is found in the V-band light of the 18 mag optical counterpart of the X-ray source. The period of the optical modulation is consistent with the X-ray dip recurr…
Serendipitous EXOSAT sources in the region of the Coma cluster : active galactic nuclei with steep X-ray spectra.
Branduardi-Raymont, G.; Mason, K. O.; Martin, C. +1 more
A ≡7-hr observation of the central part of the Coma cluster of galaxies has been performed with the EXOSAT LE telescopes and CMA detectors. Five serendipitous sources are detected within the inner 35 arcmin radius of the field. Optical spectroscopy shows that four of these are background AGN not associated with the cluster. At the sensitivity leve…
The identification of H 2311+77 with HD 220140, a probable RS CVn star.
White, N. E.; Giommi, P.; Pravdo, S. H.
H2311+77, one of the bright soft X-ray sources in the sky originally detected with HEAO 1, has been identified in an EXOSAT imaging observation with a 7.7-mag late-type star, HD 220140. The X-ray luminosity and the optical characteristics of this star indicate that it is probably an RS CVn binary system.
X-ray emission from the cataclysmic variable PG 0834+488.
Cook, M. C.
A 5-hr observation of PG0834+488 using the EXOSAT X-ray observatory has resulted in its detection as an X-ray source. The light curve shows marginal evidence for variability but no coherent periodicities were found. The X-ray spectrum was hard, with a photon index of ≡1.36, and the low-energy absorption implied a low column density NH ≡…