The pn-CCD camera on board of XMM-Newton as well as the Wide Field Imager (WFI) currently being designed for the XEUS mission can be read out in special fast timing modes, providing spectroscopy at very high time resolution. The two fast modes, Timing and Burst mode, of the pn-CCD camera on board XMM-Newton provide a time resolution of 30 μs, respectively. However, this fast timing is only possible at the expense of spatial resolution in readout direction. In contrast, the current baseline design of the WFI for XEUS will provide 25 μs timing at full spatial resolution. We describe the basic principles of the fast readout schemes of the pn-CCD and the SFI, discuss the potential of XEUS for high time resolution spectroscopy and present first results of pulse phase resolved spectroscopy of the Crab pulsar with the pn-CCD in Timing mode.

The Imager on Board of INTEGRAL (IBIS) has to cope with very high data rates (>15.000 events/sec) from two detector layers (ISGRI and PICsIT). Because the available telemetry rate is only about 130 of the expected maximum data rate an on-board data reduction and pre-processing is neccessary. This task is performed by a tailored fast Hardware Event Preprocessor (HEPI) and a slow programmable Data Processing Electronics (DPE). Several processing modes can be combined to adapt the instrument IBIS to the aims of the observers. The functions and methods of the digital on-board data processing (hardware and software) are described.

The X-ray binary pulsar Her X-1 shows a wide variety of long and short term variabilities in the X-ray light curve. The 35 d variability of the source is interpreted as the influence of a warped, inclined, and twisted accretion disk periodically covering the line of sight to the central neutron star. In 1997 September we observed the ``turn-on'' of a 35 d cycle with the Rossi X-ray Timing Explorer (RXTE). Spectral analysis reveals that during early phases of the turn-on the overall spectrum is composed of X-rays scattered into the line of sight plus heavily absorbed X-rays. This interpretation is consistent with the variation of the pulse profile observed at the same time. The overall shape of the pulse profile is not changing, but towards earlier phases of the turn-on the pulse signature is steadily ``washed out''. This behavior can be understood as an influence of scattering and absorption due to the presence of the accretion disk rim. Using a Monte Carlo code we simulate the influence of both processes on a time variable, beamed emission characteristic, similar to the pulse profile of Her X-1. By comparing the results of the simulation with the observed profiles we determine the amount of scattered radiation, absorbed radiation, and the size of the scattering region.

Recently an Anomalous Low State in the 35d cycle of Her X-l, which is thought to be caused by the tilted accretion disk, was observed with the RXTE. This has been seen only twice before; in 1983 and again 1993. We present timing and spectral results of this latest anomalous low obtained 1999 April 26. Pulsations were observed in the 2-20 keV band but with a pulsed fraction down by a factor of 10 from the main-on. Spectral analysis indicates 70% absorbed flux (N-H = 7 x 10(23)) With the remainder unabsorbed. This is consistent with continuous screening of the X-ray source by the accretion disk causing the anomalous low.

A failed main-on in the 35 day cycle of Her X-1 was observed with the Rossi X-Ray Timing Explorer on 1999 April 26. Exceptions to the normal 35 day cycle have been seen only twice before—in 1983 and again in 1993. We present timing and spectral results of this latest anomalous low state (ALS) along with comparisons to the main-on and normal low states. Pulsations were observed in the 3-18 keV band with a fractional rms variation of 0.037 ± 0.003. Spectral analysis indicates that the ALS spectrum has the same shape as the main-on but is modified by heavy absorption and scattering. We find that 70% of the observed emission has passed through a cold absorber (NH = 5.0 × 1023 cm-2). This partially absorbing spectral fit can be applied to the normal low state with similar results. We find that the ALS observations may be interpreted as a decrease in inclination of the accretion disk causing the central X-ray source to be obscured over the entire 35 day cycle.

After the launch of Chandra, it was realized that low energy protons (below approximately 300 keV) are funnelled by grazing incident mirrors onto the focal plane detectors. Front illuminated CCD detectors are very sensitive to soft protons causing radiation damage in their electrode structures and transfer channels. The back-illuminated 280 micrometer thick fully depleted pn-CCD of the European Photon Imaging Camera (EPIC) on board the X-ray Multi Mirror mission (XMM) is by far less sensitive to low energy proton radiation. Commanding the camera in a special low gain mode, even allows to directly measure proton spectra and event patterns up to 300 keV per pixel. At the 3 MV Van-de-Graaff accelerator of the Institute for Physics in Tubingen we have irradiated and tested a 3 cm2 flight-like pn-CCD with protons from 1 to 300 keV up to a fluence of 1.4 (DOT) 109 protons/cm2. This is about a factor of 1000 above the expected solar proton fluence for a 10 year XMM-Newton mission under nominal operational conditions. In this paper we given an overview of the proton irradiation experiment, discuss the performance of the detector after proton irradiation and finally present proton spectra directly measured with the pn-CCD on board XMM-Newton during solar flares. In addition, we briefly describe the precautionary measures taken to minimize the proton radiation dose of the EPIC CCD detectors in orbit.