Wolfgang Burkert

Readout modes and automated operation of the Swift X-ray Telescope

The Swift X-ray Telescope (XRT) is designed to make astrometric, spectroscopic, and photometric observations of X-ray emission from Gamma-ray Bursts and their afterglows in the energy band 0.2-10 keV. In order to provide rapid-response, automated observations of these randomly occurring objects without ground intervention, the XRT must be able to observe objects covering some seven orders of magnitude in flux, extracting the maximum possible science from each one. This requires a variety of readout modes designed to optimise the information collected in response to shifting scientific priorities as the flux from the burst diminishes. The XRT will support four major readout modes: imaging, two timing modes and photon-counting, with several sub-modes. We describe in detail the readout modes of the XRT. We describe the flux ranges over which each mode will operate, the automated mode switching that will occur and the methods used for collection of bias information for this instrument. We also discuss the data products produced from each mode.

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.

First Light Measurements of Capella with the Low-Energy Transmission Grating Spectrometer aboard the Chandra X-Ray Observatory

We present the first X-ray spectrum obtained by the Low-Energy Transmission Grating Spectrometer (LETGS) aboard the Chandra X-Ray Observatory. The spectrum is of Capella and covers a wavelength range of 5-175 Å (2.5-0.07 keV). The measured wavelength resolution, which is in good agreement with ground calibration, is Deltalambda approximately 0.06 Å (FWHM). Although in-flight calibration of the LETGS is in progress, the high spectral resolution and unique wavelength coverage of the LETGS are well demonstrated by the results from Capella, a coronal source rich in spectral emission lines. While the primary purpose of this Letter is to demonstrate the spectroscopic potential of the LETGS, we also briefly present some preliminary astrophysical results. We discuss plasma parameters derived from line ratios in narrow spectral bands, such as the electron density diagnostics of the He-like triplets of carbon, nitrogen, and oxygen, as well as resonance scattering of the strong Fe xvii line at 15.014 Å.

SWIFT XRT Point Spread Function measured at the Panter end-to-end tests

The SWIFT X-ray Telescope (XRT) is designed to make astrometric, spectroscopic and photometric observations of the X-ray emission from Gamma-ray bursts and their afterglows, in the energy band 0.2 - 10 keV. Here we report the results of the analysis of SWIFT XRT Point Spread Function (PSF) as measured during the end-to-end calibration campaign at the Panter X-Ray beam line facility. The analysis comprises the study of the PSF both on-axis and off-axis. We compare the laboratory results with the expectations from the ray-tracing software and from the mirror module tested as a single unit. We show that the measured HEW meets the mission scientific requirements. On the basis of the calibration data we build an analytical model which is able to reproduce the PSF as a function of the energy and the position within the detector.

Imaging performance of the XMM-Newton x-ray telescopes

The in-orbit imaging performance of the three X-ray telescopes on board of the X-ray astronomy observatory XMM- Newton is presented and compared with the performance measured on ground at the MPE PANTER test facility. The comparison shows an excellent agreement the on ground and in-orbit performance.

Optics for the x-ray imaging concentrators aboard the x-ray astronomy satellite SAX

The scientific instrumentation onboard the Italian satellite for x-ray astronomy (SAX) foresees x-ray imaging concentrators operating in the 0.1-10-keV energy range with a spatial resolution of 1 min of arc. The optics is composed of thirty confocal-nested very thin double-cone mirrors. To achieve good optical quality and to allow the construction of several concentrators at an acceptable cost, a replica technique by electroforming the mirrors from masters is used. This paper presents the results obtained from a set of electroformed mirrors mounted on a concentrator prototype.

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

Characteristics of the flight model optics for the JET-X telescope onboard the Spectrum-X-Gamma satellite

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In-flight calibration of the Swift XRT point spread function

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.