Search Publications
Observations of energetic particles with EPAC on Ulysses in polar latitudes of the heliosphere.
Franz, M.; Keppler, E.; Quenby, J. J. +3 more
Measurements with the EPAC energetic-charged-particle instrument aboard Ulysses show between -15° and -65° ions and, to some extent, also electrons apparently accelerated by shocks associated with a corotating interaction region (CIR) operating at low latitudes. Particles could have reached Ulysses along magnetic-field lines which connect to the s…
Low-energy interplanetary charged particles: solar south pole to solar north pole and high heliolatitudes.
Pick, M.; Anderson, K. A.; Krimigis, S. M. +9 more
Low-energy (⪆50 keV) charged particles measured by the HI-SCALE instrument on the Ulysses spacecraft provided unique information on the particle composition and intensity in both polar regions of the Sun. Further, the rapid 160° south-to-north solar transit of Ulysses in early 1995 yielded new information on heliospheric structure. This paper revi…
Interstellar extinction: a parametrical study by using laboratory data.
Mennella, V.; Colangeli, L.; Rotundi, A. +2 more
The authors present a comparative study between laboratory data, astronomical observations and theoretical models in order to provide a contribution to the characterization of cosmic-dust properties. In particular, they propose a parametrization of the amorphous-carbon extinction curve. The laboratory extinction measurements, performed in the extr…
How robust are the EGRET AGN gamma-ray identifications?
Bignami, G. F.; Caraveo, P.; Ciliegi, P.
Several AGNs have been proposed as identifications of gamma-ray sources discovered by CGRO. Using the NED database, the authors show that these AGNs are not the only extragalactic objects within the error boxes of the sources. Therefore, an in-depth study is needed on a case-by-case basis to access the most probable counterparts of the gamma-ray s…
The Ulysses space mission.
Poletto, G.; Noci, G.; Monsignori Fossi, B. C.
The authors describe briefly the collaborative ESA-NASA Ulysses mission which will provide, for the first time in the history of the solar-system exploration, in situ observations of the heliosphere over a broad range of heliographic latitudes. Launched on October 6, 1990, Ulysses has been injected in a high-inclination orbit by means of a gravity…
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…