Search

We present XMM-Newton Reflection Grating Spectrometer observations of X-ray clusters and groups of galaxies. We demonstrate the failure of the standard cooling-flow model to describe the soft X-ray spectrum of clusters of galaxies. We also emphasize several new developments in the study of the soft X-ray spectrum of cooling flows. Although there is some uncertainty in the expected mass deposition rate for any individual cluster, we show that high resolution RGS spectra robustly demonstrate that the expected line emission from the isobaric cooling-flow model is absent below 1/3 of the background temperature rather than below a fixed temperature in all clusters. Furthermore, we demonstrate that the best-resolved cluster spectra are inconsistent with the predicted shape of the differential luminosity distribution and the measured distribution is tilted to higher temperatures. These observations create several fine-tuning challenges for current theoretical explanations for the soft X-ray cooling-flow problem. Comparisons between these observations and other X-ray measurements are discussed., Comment: 6 pages, 8 figures; Contribution for "The Riddle of Cooling Flows in Galaxies and Clusters of Galaxies", eds. Reiprich, T. H., Kempner, J. C., & Soker, N., Charlottesville, VA, USA, May 31-June 4, 2003, proceedings at http://www.astro.virginia.edu/coolflow

In a recent Letter, Berghoefer & Bowyer rediscussed the analysis of BeppoSAX LECS data of the cluster of galaxies Abell 2199 as presented by Kaastra et al., in particular the detection of a soft X-ray excess. Berghoefer & Bowyer stated that their analysis method is better suited and does not show evidence for a soft X-ray excess. Here we find it necessary to publish a rebuttal, because it can be demonstrated that the method used by Berghoefer & Bowyer is oversimplified, leading to an erroneous result. As a consequence, their statement that our initial analysis is incorrect is invalid and the detection of a soft X-ray excess in A 2199 is still confirmed., Comment: 6 pages, accepted for publication in The Astrophysical Journal, Letters

We present BeppoSAX X-ray spectra of the remnant of the supernova of AD 1006, which cover a broad spectral range of 0.1-10 keV. In our analysis we concentrate on the thermal emission from the central region of the remnant. For this purpose we fitted the spectra of the whole remnant using a new version of the spectral program SPEX, which takes into account the interdependence of spectra of different regions as the result of the point spread function of the instruments. This is in particular important for separating the synchrotron emission, coming from the bright rims of the remnant, from the thermal emission from the central regions. The thermal emission appears best fitted with a combination of two spectral components with electron temperatures of about 0.7 keV and more than 3 keV. The plasma in SN 1006 appears to be very far out of ionization equilibrium (nt = 2 10^15 m^-3 s), which means that the L-shell emission of magnesium, silicon and sulphur contribute significantly to the flux below 0.5 keV. We also note the presence of Fe K line emission at 6.3+/-0.2 keV, in agreement with an origin from inner shell ionizations and excitations. We confirm that the abundances in SN 1006 are clearly non-solar. In particular silicon is very abundant. We did not find substantial variations in plasma properties over the face of the remnant, although the hotter component seems more dominant in the Northern half of the remnant., Comment: 7 page, 3.5 figures; the first figure is a seperate GIF file; Accepted by Astronomy and Astrophysics, main journal

We present an analysis of the BeppoSAX high X-ray energy spectrum of the supernova remnant Cassiopeia A with an observation time of 83 ks. We measure a flux upper limit of 4.1E-5 ph/cm^2/s (99.7% confidence) of the nuclear decay lines of Ti-44 at 68 keV and 78 keV that is lower and inconsistent with the flux of an accompanying line at 1157 keV measured by CGRO's Comptel. However, if the underlying X-ray continuum is lower, because the spectrum is steepening, the actual Ti-44 flux may be higher and consistent with the Comptel result, although the measured flux of (2.9 +/- 1.0)E-5 ph/cm^2/s under this assumption is still lower than the flux measured by Comptel., Comment: ; JVs present address: AIP, Potsdam (jvink@aip.de). To be published in Advances of Space Research (proc. of the Cospar Conference, Nagoya, 1998). 6 pages, 3 figures

We report the detection of both soft and hard excess X-ray emission in the cluster of galaxies A 2199, based upon spatially resolved spectroscopy with data from the BeppoSAX, EUVE and ROSAT missions. The excess emission is visible at radii larger than 300 kpc and increases in strength relative to the isothermal component. The total 0.1-100 keV luminosity of this component is 15 % of the cluster luminosity, but it dominates the cluster luminosity at high and low energies. We argue that the most plausible interpretation of the excess emission is an inverse Compton interaction between the cosmic microwave background and relativistic electrons in the cluster. The observed spatial distribution of the non-thermal component implies that there is a large halo of cosmic ray electrons between 0.5-1.5 Mpc surrounding the cluster core. The prominent existence of this component has cosmological implications, as it is significantly changing our picture of a clusters's particle acceleration history, dynamics between the thermal and relativistic media, and total mass budgets., Comment: Accepted for publication in Astrophysical Journal, Letters

We present deconvolved narrow band images of Cas A as observed by the MECS instrument on the BeppoSAX X-ray satellite. The images show that Cas A has different morphologies in the continuum and line bands. This difference points towards a synchrotron origin for part of the X-ray continuum of Cas A. Going to the hardest continuum band we find that the emission is coming predominantly from the Western region, making this the most likely location for the hard X-ray tail seen with instruments on CGRO (OSSE), BeppoSAX (PDS) and RXTE (HEXTE)., Comment: 7 pages, 7 figures, accepted by Astronomy and Astrophysics, see http://www.sron.nl/~jaccov for a color version of figure 3