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Coordinated observation of the massive system 4U 1700+24 = HD 154791.

Frontera, F.; Manzo, G.; Robba, N. R. +7 more

The authors report results from multifrequency observations of the X-ray source 4U 1700+24 / HD 154791. This source was observed simultaneously with the EXOSAT and IUE satellites on March 25, 1985, and it is continuously monitored in the optical band at the Bologna Astronomical Observatory since July 1984. Their observations show source features w…

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…

EXOSAT observation of 'Geminga'

Caraveo, P. A.; Bignami, G. F.

IE 0630 + 178, the X-ray source associated with the gamma-ray source Geminga (2CG195 + 04), has been observed by the EXOSAT satellite. The X-ray images, recorded by the channel-multiple-array instruments at the foci of the two low-energy telescopes equipped with different filters, show clearly the source. The flux value, computed from the count ra…

Broad-band X-ray spectrum of the bright Seyfert galaxy MKN 509

Molteni, D.; Robba, N. R.; Sacco, B. +1 more

One of the brightest X-ray Seyfert galaxies, Mkn 509, has been observed with the X-ray satellite EXOSAT. Wide-band (0.05 - 35 keV) spectral information is now available at the same time. Different filters have been rotated in front of the low-energy telescope. The overall spectrum is best fitted by a two-component power law. The intensity and the …

The EXOSAT and Einstein observations of 1E0630 + 178 ('Geminga') as complementary data sets

Caraveo, P. A.; Bignami, G. F.; Mereghetti, S. +1 more

Data for the soft X-ray source 1E0630 + 178 are now available from four independent measurements of the Einstein and EXOSAT missions. These are presented and compared in the light of the different characteristics and energy response of the different X-ray imaging detectors used (IPC, LE 1, LE 2). The time variability on medium (hours) time scale i…

Evidence for an increasing 59 S period in the X-ray emission from Geminga

Caraveo, P. A.; Bignami, G. F.; Salotti, L.

Einstein Observatory and EXOSAT X-ray data from 1E0630 + 178 reveal an approximately 50-percent periodic emission at about 59 s or more. This confirms the early SAS-II and COS-B findings on 2CG 195 + 04 at E greater than 50 MeV and provides the temporal signature for the identification of Geminga. The observations, spanning over a decade (1973-198…