A setup for soft proton irradiation of X-ray detectors for future astronomical space missions

Protons that are trapped in the Earth's magnetic field are one of the main threats to astronomical X-ray observatories. Soft protons, in the range from tens of keV up to a few MeV, impinging on silicon X-ray detectors can lead to a significant degradation of the detector performance. Especially in low earth orbits an enhancement of the soft proton flux has been found. A setup to irradiate detectors with soft protons has been constructed at the Van-de-Graaff accelerator of the Physikalisches Institut of the University of T\"ubingen. Key advantages are a high flux uniformity over a large area, to enable irradiations of large detectors, and a monitoring system for the applied fluence, the beam uniformity, and the spectrum, that allows testing of detector prototypes in early development phases, when readout electronics are not yet available. Two irradiation campaigns have been performed so far with this setup. The irradiated detectors are silicon drift detectors, designated for the use on-board the LOFT space mission. This paper gives a description of the experimental setup and the associated monitoring system.Comment: 20 pages, 10 figures, 4 table

XMM-EPIC observation of MCG-6-30-15: Direct evidence for the extraction of energy from aspinning black hole?

We present XMM-Newton European Photon Imaging Camera (EPIC) observations of the bright Seyfert 1 galaxy MCG-6-30-15, focusing on the broad Fe K$\alpha$ line at ~6keV and the associated reflection continuum, which is believed to originate from the inner accretion disk. We find these reflection features to be extremely broad and red-shifted, indicating its origin from the very most central regions of the accretion disk. It seems likely that we have caught this source in the ``deep minimum'' state first observed by Iwasawa et al. (1996). The implied central concentration of X-ray illumination is difficult to understand in any pure accretion disk model. We suggest that we are witnessing the extraction and dissipation of rotational energy from a spinning black hole by magnetic fields connecting the black hole or plunging region to the disk.Comment: 6 pages and one postscript figure. Accepted for publication in MNRAS letter

Improving XMM-Newton EPIC pn data at low energies: method and application to the Vela SNR

High quantum efficiency over a broad spectral range is one of the main properties of the EPIC pn camera on-board XMM-Newton. The quantum efficiency rises from ~75% at 0.2 keV to ~100% at 1 keV, stays close to 100% until 8 keV, and is still ~90% at 10 keV. The EPIC pn camera is attached to an X-ray telescope which has the highest collecting area currently available, in particular at low energies (more than 1400 cm2 between 0.1 and 2.0 keV). Thus, this instrument is very sensitive to the low-energy X-ray emission. However, X-ray data at energies below ~0.2 keV are considerably affected by detector effects, which become more and more important towards the lowest transmitted energies. In addition to that, pixels which have received incorrect offsets during the calculation of the offset map at the beginning of each observation, show up as bright patches in low-energy images. Here we describe a method which is not only capable of suppressing the contaminations found at low energies, but which also improves the data quality throughout the whole EPIC pn spectral range. This method is then applied to data from the Vela supernova remnant.Comment: Proc. SPIE Vol. 5488: Astronomical Telescopes and Instrumentation, UV - Gamma-Ray Space Telescope Systems, Eds. Guenther Hasinger and Martin J. Turner, 22-24 June 2004, Glasgow, Scotland United Kingdo

On the deep minimum state in the Seyfert galaxy MCG-6-30-15

(abridged) We present a detailed spectral analysis of the first observation of the Seyfert 1 galaxy MCG-6-30-15 by the European Photon Imaging Camera on board the XMM-Newton observatory, together with contemporaneous data from the Proportional Counter Array on the Rossi X-ray Timing Explorer. Confirming our previously published result, we find that the presence of extremely broadened reflection features from an ionized relativistic accretion disk is required even when one employs the latest X-ray reflection models and includes the effect of complex absorption. The extremely broadened reflection features are also present if the primary continuum is modeled with a thermal Comptonisation spectrum rather than a simple power-law continuum. With this fact established, we examine these data using a relativistic smearing function corresponding to a ``generalized thin accretion disk'' model. We find strong evidence for torquing of the central parts of the accretion disk (presumably through magnetic interactions with the plunging region of the disk and/or the rotating black hole itself). We also perform a study of spectral variability within our observation. We find that the disk reflection features maintain roughly a constant equivalent width with respect to the observed continuum, as predicted by simple reflection models. Taken together with other studies of MCG-6-30-15 that find disk features to possess constant intensity at higher flux states, we suggest that the flux of disk features undergoes a saturation once the source emerges from a Deep Minimum state.Comment: 16 pages, accepted for publication in MNRA