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Coordinated X-ray and ultraviolet observations of the intermediate polar H2215-086
Maraschi, L.; Tanzi, E. G.; Chiappetti, L. +6 more
Quasi-simultaneous observations of H2215-086 (=FO Aqr), obtained with Exosat and IUE in 1983 and 1985 are reported. Secular variations in the X-ray flux and in the shape of the rotational light curve are observed. The modulation of the photoelectric absorption cutoff is studied by means of phase resolved X-ray spectra. A possible orbital modulatio…
IUE and optical spectrophotometry of the HZ Herculis/Hercules X-1 system
Howarth, I. D.; Raymond, J. C.; Wilson, R. +1 more
Photometric (B-filter) data of HZ Herculis obtained between 1972 and 1974 have been fitted by a model consisting of Roche-lobe-filling star transferring material to a neutron star via a tilted, preccessing, accretion disc. The disc inclination was found to be small, thus avoiding theoretical difficulties experienced with high-inclination discs. We…
Optical and UV observations of the symbiotic star CH Cygni after the jets ejection in 1984
Mikolajewska, J.; Mikolajewski, M.; Tomov, T.
The optical and UV observations of the symbiotic star CH Cyg are discussed in the context of the jet appearance. CH Cygni is an eclipsing binary with a period of 5700 days, consisting of an M 6 giant and a white dwarf surrounded by an accretion disk formed from the cool giant wind. Previous studies of the system are reviewed and emission line prof…
The dwarf nova dippers
Sonneborn, G.; Charles, P. A.; Hassall, B. J. M. +1 more
Two previous papers /1,2/ have shown that the dwarf nova OY Car has extensive vertical disc structure during its (~2 week) superoutbursts. This structure is analogous to that seen in the low mass X-ray binaries (LMXBs), in that the whole disc flares towards its edge, and there is a bulge or ``dark spot'' where the mass transfer stream meets the di…
Energy distribution and variability of BL Lac objects: Recent observations and a theoretical scheme
Maraschi, L.
Spectral properties of X-ray selected and radio-selected BL Lacs are discussed. The results provide a direct indication that the X-ray emission is more isotropic than the radio emission. Recent results of multifrequency observations of the brightest X-ray selected BL Lac object, PKS 2155-304, are reviewed, showing how the fast X-ray variability is…
SS Cygni: The mass accretion rate behaviour in quiescence and in outburst
Gaudenzi, S.; Giovannelli, F.; Claudi, R. +1 more
From the HeII λ1640 emission line equivalent width values in all good available IUE low resolution spectra, we have deduced the correspondent mass accretion rate values Mdot for SS Cygni, using the optically thick boundary-layer model by Patterson and Raymond 1985. The Mdot behaviour can be distinguished as follows:
1) in the rising and decli…Infrared to UV energy distribution of the black hole candidate LMC X-3: Observation of the accretion disk
Maraschi, L.; Tanzi, E. G.; Chiappetti, L. +4 more
LMC X-3 is a binary X-ray source which most probably hosts a black hole. Here, the authors present a preliminary report on observations of the source in the IR, optical, and UV bands. The observations allow to evidentiate the presence of the accretion disk surrounding the black hole.