Elmar Pfeffermann

The ROSAT all - sky survey bright source catalogue

In order to ensure the quality of the source catalogue derived from the SASS processing an automatic as well as a visual screening procedure was applied to 1378 survey fields. Most (94%) of the 18,811 sources were confirmed by this screening process. The rest is flagged for various reasons. Broad band images are available for a subset of the flagged sources. Details of the screening process can be found at www.rosat.mpe-garching.mpg.de/survey/rass-bsc/doc.html.

Performance of the pn-CCD X-ray detector system designed for the XMM satellite mission

Abstract The pn-CCD detector system is designed as a focal plane instrument for the European Photon Imaging Camera (EPIC) on the X-ray Multi Mirror mission (XMM) of the European Space Agency. This satellite will be launched by the end of this century. The sensitive area of the detector consists of a 6 × 6 cm2 array of 12 pn-CCDs monolithically integrated on a single silicon wafer. The detector has been optimized for high-resolution X-ray spectroscopy between 100 eV and 15 keV with simultaneous good quantum efficiency for the investigation of faint objects. A fast readout achieves excellent time resolution for the observation of pulsed X-ray sources. The relevant performance parameters reflecting the state of the detector development are presented. Energy resolution reaches the theoretical limits given by the Fano noise. Due to a thin entrance window and full depletion of the device the quantum efficiency is better than 80% over a wide energy range. Evidence for radiation hardness and background rejection capability will also be provided.

eROSITA on SRG

eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the core instrument on the Russian Spektrum-Roentgen-Gamma (SRG) mission which is scheduled for launch in late 2012. eROSITA is fully approved and funded by the German Space Agency DLR and the Max-Planck-Society. The instrument development is in phase C/D since fall 2009. The design driving science is the detection 100.000 Clusters of Galaxies up to redshift z ~1.3 in order to study the large scale structure in the Universe and test cosmological models, especially Dark Energy. This will be accomplished by an all-sky survey lasting for four years plus a phase of pointed observations. eROSITA consists of seven Wolter-I telescope modules, each equipped with 54 Wolter-I shells having an outer diameter of 360 mm. This would provide an effective area of ~1500 cm2 at 1.5 keV and an on axis PSF HEW of 15 arcsec resulting in an effective angular resolution of 28 - 30 arcsec, averaged over the field of view. In the focus of each mirror module, a fast frame-store pn-CCD provides a field of view of 1° in diameter.

The first broad-band X-ray images and spectra of the 30 Doradus region in the LMC

We present the XMM-Newton first light image, taken in January 2000 with the EPIC pn camera during the instruments commissioning phase, when XMM-Newton was pointing towards the Large Magellanic Cloud (LMC). The field is rich in different kinds of X-ray sources: point sources, supernova remnants (SNRs) and diffuse X-ray emission from LMC interstellar gas. The observations are of unprecedented sensitivity, reaching a few 10

The EPIC pn-CCD detector aboard XMM-Newton: status of the background calibration

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The position sensitive proportional counter (PSPC) of the Rosat telescope

erg/s for point sources in the LMC. We describe how these data sets were analysed and discuss some of the spectroscopic results. For the SNR N157B the power law spectrum is clearly steeper than previously determined from ROSAT and ASCA data. The existence of a significant thermal component is evident and suggests that N157B is not a Crab-like but a composite SNR. Most puzzling is the spectrum of the LMC hot interstellar medium, which indicates a significant overabundance of Ne and Mg of a few times solar.

pnCCDs on XMM-Newton-42 month in orbit

We report on the current status of the background calibration of the EPIC pn-CCD camera on board XMM-Newton. The intrinsic background is comprised of internal electronic noise, and continuous and fluorescent X-ray emission induced by high-energy particles. Soft protons passing through the X-ray telescope (and finally also true cosmic X-rays) contribute to the registered events. The camera background has been monitored by using data in closed filter positions for three years; we review the spectral, spatial, and temporal distribution, for all commissioned instrument modes. This paper also discusses briefly the effects on scientific data analysis and conclusions for further observations and detectors.

The Rosat mission

Abstract A position sensitive proportional counter for X-rays in the energy range from 0.1 to 2.0 keV has been developed and tested. It is the prime focal instrument of the Rosat X-ray telescope, a satellite-observatory, which will be launched in 1987. Over the entire sensitive circular area of 80 mm diameter, the energy resolution for 0.93 keV X-rays is 45%. Local deviations of the gas gain from the mean value is less than 3%. For X-ray energies of 0.93 and 0.28 keV, the mean position resolution is 250 and 400 μm (fwhm) respectively. When correcting the position of each X-ray event, we achieve differences between the nominal and the measured position of pinholes of less than 20 μm. Operating the PSPC in the environment of a 60 Co gamma-ray source, we measured an overall background rejection of more than 99%.

Systematic testing and results of X-ray CCDs developed for eROSITA and other applications

Abstract XMM-Newton—a cornerstone mission of the European Space Agencys Horizon 2000 programme—was launched on December 10, 1999 into orbit. Since March 2000 more than 2000 scientific observations were made. An example will be shown. The X-ray pnCCD camera on EPIC is operating since then without severe problems. We will report about the system performance as a function of time, with special emphasis on the effect of radiation damage in orbit. Up to now the spectroscopic and imaging performance of the pnCCD camera system is stable with time, even at the lowest energies most sensitive to degradation. The deviations of the detector response compared to the prelaunch performance over the 3.5 years is below 0.5%. One year after launch, the pnCCD X-ray camera was hit by a micrometeoroid, damaging 35 pixels spread over the entire field of view. Details of the impact of the pnCCD with a cosmic dust particle will be given. X-ray fluorescence photons, stimulated by charged particles, constitute a significant part of the instrument background. Possible improvements for future missions will be discussed.

PN-CCD camera for XMM: performance of high time resolution/bright source operating modes

The primary scientific objective of the ROSAT mission is to perform the first all sky survey with an imaging X-ray telescope leading to an improvement in sensitivity by several orders of magnitude compared with previous surveys. Consequently a large number of new sources (> 105) will be discovered and located with an accuracy of 1 arcmin. After completion of the survey which will take about half a year the instrument will be used for detailed observations of selected targets.The X-ray telescope consists of a fourfold nested Wolter type I mirror system with 80 cm aperture and 240 cm focal length, and three focal plane detectors. In the baseline version these will be imaging proportional counters (0.1 – 2 keV) providing a field of view of 20 × 20.