Search Publications
Variability in the noise properties of Cygnus X-1.
Belloni, T.; Hasinger, G.
The aperiodic variability in the X-ray emission of Cyg X-1 is examined from 13 Exosat observations covering the period July 1983 - October 1985, by means of broad band 0.001-100 H3 power spectra. The total rms fractional variations in the range 0.016-14 Hz is between 28 and 38 percent. The power distribution is flat below a characteristic break fr…
An atlas of aperiodic variability in HMXB.
Belloni, T.; Hasinger, G.
From EXOSAT archive data of 14 X-ray binaries (12 high mass X-ray binaries and 2 low mass X-ray binaries) broad band power spectra and color- color diagrams are produced. The aperiodic (noise) variability of the sources is studied. All the X-ray pulsars present in the sample show strong noise components in the emission, with a fractional variabili…
X-ray emission from solar neighbourhood flare stars : a comprehensivesurvey of EXOSAT results.
Tagliaferri, G.; Stella, L.; Pallavicini, R.
Exosat Observatory observations of flare stars pertaining to 25 separate sources are examined. The Exosat instrumentation is described, and a data sample is presented. Quiescent and flaring emissions from UV Ceti-type flare stars as observed with a low-energy experiment on Exosat are discussed, and the results of the timing analysis of the low-ene…
The ultraviolet and X-ray spectrum of NGC 5548 : evidence for thermal Comptonization and geometrical variations.
Walter, R.; Courvoisier, T. J. -L.
Ultraviolet, soft and hard X-ray observations of NGC 5548 performed by IUE and EXOSAT give us a clear picture for the geometry of the emitting source. This picture is provided by the correlations observed between the large variations of the ultraviolet continuum, of the soft and hard X-ray fluxes, of the hard X-ray powerlaw index and of the equiva…
Rotational modulation and flares on RS Canum Venaticorum and BY Draconis-type stars. XIV. Phasen eclipse and flare observations of YY Geminorum by EXOSAT and IUE.
Schmitt, J. H. M. M.; Rodono, M.; Haisch, B. M. +1 more
The eclipsing spectroscopic binary YY Geminorum has been observed at optical, ultraviolet, and X-ray wavelengths for rotational modulation, eclipse variability, and flaring. The epoch T(phi = 0) = JD 2425698.3561, and the phase P = 0.81428224 d. The quiescent level of Mg II emission is remarkably steady during the three-year observing interval, wi…
An X-ray flare observed from van Biesbroeck 8.
Tagliaferri, G.; Doyle, J. G.; Giommi, P.
An X-ray flare was detected on the previously unknown flare-star van Biesbroeck 8 ( = Gl 644 C). The total energy of the event in the 0.05-2 keV energy range was 8 x 10 to the 31st erg/s with a mean luminosity of 1.8 x 10 to 28th erg/s. This implies an emission measure of about 6 x 10 to the 50th/cu cm, and adopting a simple loop model an electron…
Rotational modulation and flares on RS Canum Venaticorum and BY Draconis-type stars. XV. Observations of Proxima Centauri and solar calibration data.
Foing, B.; Rodono, M.; Butler, C. J. +2 more
Results are reported from simultaneous Exosat and IUE observations of flaring in Proxima Cen on March 2, 1985. The data are presented in extensive tables and sample spectra and discussed in detail. The peak emission of the soft-X-ray flare is found to be about 3 x 10 to the 27th erg/sec, with energy about 3 x 10 to the 30th erg and an associated i…
Flaring and quiescent X-rays from Castor.
Schmitt, J. H. M. M.; Tagliaferri, G.; Pallavicini, R. +2 more
Using data obtained with the Low Energy (LE) and Medium Energy instruments aboard Exosat, the first detection of both flaring and quiescent X-ray emission from the A-type visual binary Castor (alpha Gem) is reported. In the LE, Castor was clearly resolved from the nearby star YY Gem, which was also observed to flare some hours after Castor. After …
EXOSAT observations of a long X-ray burst from XB 1905+000.
Ilovaisky, S. A.; Chevalier, C.
During a 17-hour continuous Exosat observation of the faint X-ray source XB 1905 + 000 a single burst was detected which shows a long decay following a radius expansion-contraction phase near maximum bolometric flux. The best spectral fits for the persistent emission are found when a 10-percent contribution from a cool blackbody component is added…
EXOSAT observation of the supernova remnant MSH 15-52.
Hasinger, G.; Aschenbach, B.; Brinkmann, W. +3 more
The results of an Exosat observation of the supernova remnant MSH 15-52 and of the pulsar PSR 1509-58 are presented and discussed. In the energy range 1.6-11 keV, the radiation flux of the nebula surrounding the pulsar detected by the ME instrument has been fitted with a power law spectrum with index alpha about 1.86 (photon spectrum) and column d…