Search Publications
The broad band energy distribution of UV-bright BL Lac objects
Maraschi, L.; Tanzi, E. G.; Treves, A.
Renewed attention was paid to the study of the continuous energy distribution of BL Lac objects, bearing on the emission mechanisms of the central source, since the launch of the International Ultraviolet Explorer (IUE). The far ultraviolet domain (1000 - 3000 Å) is in fact particularly relevant to the problem, because it does not suffer from cont…
Ultraviolet spectroscopy of cometary comae: An update
Feldman, P. D.
Since its launch in 1978 the International Ultraviolet Explorer (IUE) satellite observatory has been used to record ultraviolet spectra of nearly two dozen comets. These observations have been applied principally to studies of the composition, chemistry and evolution of the gaseous coma and more recently, with the substantially increased data base…
Rapid short-term pulse-period variations in Vela X-1 (4U 0900-40)
van der Klis, M.; Bonnet-Bidaud, J. M.
Results are presented of an analysis of 83 days of 2-12 keV X-ray observations of Vela X-1 (4U 0900-40) obtained during three separate pointings with the ESA COS-B satellite. The pulsation period is shown to undergo very rapid intrinsic changes, at a rate of up to P˙/P ~ 10-1 yr-1 during intervals of a few days. The lower val…
The radial distribution of gamma rays and cosmic rays in the outer Galaxy
Hermsen, W.; Bloemen, J. B. G. M.; Blitz, L.
The radial distribution of the high-energy (70 MeV-5 GeV) gamma-ray emissivity in the outer Milky Way is derived. The kinematics of HI are used to construct column-density maps in three galacto-centric distance ranges in the outer Galaxy. These maps are used in combination with COS-B gamma-ray data to determine gamma-ray emissivities in these dist…
The galactic distribution of cosmic-ray particles
Hermsen, W.; Bloemen, J. B. G. M.
COS-B gamma-ray observations are compared with large-scale HI and CO surveys in different regions of the sky to derive information on the cosmic-ray density distribution throughout the Galaxy and/or a calibration of the ratio between H2 column density and integrated CO line intensity [N(H2)/Wco]. In the region of t…
Background-sensitive event selection in the search for gamma-ray sources
Özel, M. E.; Mayer-Haßelwander, H. A.
Poor angular resolution of present day gamma ray telescopes (1° at 100 MEV) together with the complicated gamma ray sky structures at compareable angular extents and poor statistics available necessitate the selection of those gammas which will increase the observable signal from a suspected source. A method for such a selection using the pre-know…
The EXOSAT mission - Status and early results
Taylor, B. G.; Peacock, A.; Andresen, R. D.
The status of the EXOSAT programme, during the calibration and performance verification phase, is summarised and some highlight results from this phase are presented.
Active stars and systems
Rodono, M.
The most notable manifestations of stellar activity are reviewed with particular emphasis on the merging picture of solar-type activity in physical conditions different from those in the Sun. Evidence for starspots, plages and high-level coronal emissions is presented from observations covering a wide range of spectral bands: from X-ray to radio w…
X-ray diagnostics of globular clusters
Grindlay, J. E.
The presence of compact X-ray sources in globular clusters allows diagnostic studies of both the X-ray sources themselves and the globular clusters to be carried out. A review of much of this work, primarily based on Einstein X-ray observations and supporting studies of globular clusters at radio through UV wavelengths, is presented. The compact X…
IUE observations of globular clusters and blue horizontal branch stars
Code, A. D.
This paper presents a review of ultraviolet photometry and spectroscopy of globular clusters and blue horizontal branch stars. Current observations with IUE are placed within the framework of earlier photometric studies carried out by OAO and ANS. In order to provide basic information on the nature of the horizontal branch star, whose light domina…