BeppoSAX and ASCA observations of the nearby (z = 0.184), high–luminosity, radio-quiet quasar PDS 456 are presented. The X–ray spectrum is characterized by a prominent ionized edge at 8–9 keV (originally discovered by RXTE, Reeves et al. 2000) and by a soft excess below 1.5 keV. The lack of any significant iron Kα emission line suggests for the edge an origin from line–of–sight material rather ...

We report on low-resolution spectroscopy of GX339–4 during its current, extended X-ray 'off' state in May 2000 (r=20.1) obtained with the VLT Focal Re-ducer/low dispersion Spectrograph (FORS1). Although we do not positively detect the secondary star in GX339–4 we place an upper limit of 30 percent on the contribution of a " normal " K-type secondary star spectrum to the observed flux. Using thi...

We present the first unambiguous case of external variability of a radio gravitational lens, CLASS B1600+434. The Very Large Array (VLA) 8.5–GHz difference light curve of the lensed images, taking the proper time-delay into account, shows the presence of external variability with 14.6–σ confidence. We investigate two plausible causes of this external variability: scattering by the ionized compo...