1,902 research outputs found
The XMM-Newton EPIC Background and the production of Background Blank Sky Event Files
We describe in detail the nature of XMM-Newton EPIC background and its
various complex components, summarising the new findings of the XMM-Newton EPIC
background working group, and provide XMM-Newton background blank sky event
files for use in the data analysis of diffuse and extended sources. Blank sky
event file data sets are produced from the stacking of data, taken from 189
observations resulting from the Second XMM-Newton Serendipitous Source
Catalogue (2XMMp) reprocessing. The data underwent several filtering steps,
using a revised and improved method over previous work, which we describe in
detail. We investigate several properties of the final blank sky data sets. The
user is directed to the location of the final data sets. There is a final data
set for each EPIC instrument-filter-mode combination.Comment: Paper accepted by A&A 22 December 2006. 14 pages, 8 figures. Paper
can also be found at http://www.star.le.ac.uk/~jac48/publications
In-orbit Vignetting Calibrations of XMM-Newton Telescopes
We describe measurements of the mirror vignetting in the XMM-Newton
Observatory made in-orbit, using observations of SNR G21.5-09 and SNR
3C58 with the EPIC imaging cameras. The instrument features that complicate
these measurements are briefly described. We show the spatial and energy
dependences of measured vignetting, outlining assumptions made in deriving the
eventual agreement between simulation and measurement. Alternate methods to
confirm these are described, including an assessment of source elongation with
off-axis angle, the surface brightness distribution of the diffuse X-ray
background, and the consistency of Coma cluster emission at different position
angles. A synthesis of these measurements leads to a change in the XMM
calibration data base, for the optical axis of two of the three telescopes, by
in excess of 1 arcminute. This has a small but measureable effect on the
assumed spectral responses of the cameras for on-axis targets.Comment: Accepted by Experimental Astronomy. 26 pages, 18 figure
Strength of non-traditional granular materials assessed from drained multistage triaxial tests
When granular materials are applied in geotechnical works, like embankments and road pavement layers, one of the most relevant engineering properties in stability analysis is ultimate shear strength. In geotechnical engineering, the triaxial test is one of the most reliable methods available for determining ultimate shear strength. In this test, a soil specimen, compacted in laboratory or collected from exploratory soil borings, is generally used. In order to determine the strength parameters, at least 3 identical specimens are required in this test. Having 3 identical specimens, a single stage triaxial test procedure is used. If not, multistage triaxial test procedure is used to eliminate the effects of soil variability in the results. In this case, several confining pressures are applied to the same specimen. Although multistage triaxial tests have been used for soils for a long time, there is still a lack of test results for unbound granular non-traditional materials. This paper presents triaxial test results obtained from a Portuguese unbound granular non-traditional material (named as Inert Steel Aggregate for Construction - ISAC). The triaxial tests were carried out using multistage and single stage techniques. As the results are quite well comparable, it is concluded that it is possible to determine shear strength parameters with just one specimen. Consequently, the research conducted has validated the use of multistage triaxial tests as a reliable and cost-effective alternative to the conventional single stage triaxial test in the mechanical characterization of unbound granular materials.The authors appreciate the financial support of the FCT for this project PCDT/ECM/56952/2004 through the POCI 2010 program and for the cohesion fund FEDER and a doctoral grant within company SFRH/BDE/15661/2007. Acknowledgments are also due to AntĂłnio Cavalheiro, deputy manager of the Seixal Iron Steel Company.info:eu-repo/semantics/publishedVersio
Constituents of the soft X-ray background
The X-ray background is generated by various classes of objects and variety
of emission mechanisms. Relative contribution of individual components depends
on energy. The goal is to assess the integral emission of the major components
of the soft X-ray background (extragalactic discrete sources dominated by AGNs,
galactic plasma, and the Warm/Hot Intergalactic Medium), investigating the
angular structure of the background. Fluctuations of the background are
measured using the auto-correlation function of the XRB determined in 5 energy
bands between 0.3 and 4.5 keV. The investigation is based on the extensive
observational data set selected from the XMM-Newton archives. Amplitudes of the
auto-correlation functions calculated in three energy bands above ~1 keV are
consistent with the conjecture that the background fluctuations result solely
from clustering of sources which produce the background. At energies below 1
keV the relative fluctuation amplitude decreases indicating that a fraction of
the soft XRB is associated with a smooth plasma emission in the Galaxy. It is
shown, however, that the mean spectrum of extragalactic discrete sources
steepens in the soft X-rays and is not well represented by a single power law
in the energy range 0.3-4.5 keV. The WHIM contribution to the total background
fluctuations is small and consistent with the WHIM properties derived from the
cross-correlation of the XRB with galaxies.Comment: 7 pages, 2 figure
An XMM and Chandra view of massive clusters of galaxies to z=1
The X-ray properties of a sample of high redshift (z>0.6), massive clusters
observed with XMM-Newton and Chandra are described, including two exceptional
systems. One, at z=0.89, has an X-ray temperature of T=11.5 (+1.1, -0.9) keV
(the highest temperature of any cluster known at z>0.6), an estimated mass of
(1.4+/-0.2)x10^15 solar masses and appears relaxed. The other, at z=0.83, has
at least three sub-clumps, probably in the process of merging, and may also
show signs of faint filamentary structure at large radii,observed in X-rays. In
general there is a mix of X-ray morphologies, from those clusters which appear
relaxed and containing little substructure to some highly non-virialized and
probably merging systems. The X-ray gas metallicities and gas mass fractions of
the relaxed systems are similar to those of low redshift clusters of the same
temperature, suggesting that the gas was in place, and containing its metals,
by z=0.8. The evolution of the mass-temperature relation may be consistent with
no evolution or with the ``late formation'' assumption. The effect of point
source contamination in the ROSAT survey from which these clusters were
selected is estimated, and the implications for the ROSAT X-ray luminosity
function discussed.Comment: 9 pages, in Carnegie Observatories Astrophysics Series, Vol. 3:
Clusters of Galaxies: Probes of Cosmological Structure and Galaxy Evolution,
ed. J. S. Mulchaey, A. Dressler, and A. Oemler. See
http://www.ociw.edu/ociw/symposia/series/symposium3/proceedings.html for a
full-resolution versio
Soils of Day County South Dakota
The soil map, in the folder attached to the back cover of this bulletin, has been divided into two sections, the eastern half and the western half. These maps show the distribution of different soils that occur in the county. In the text, recommendations as to the use, management, and conservation are made in an attempt to answer the major questions of the farmers and others interested in the soils of Day County
Discovery of complex narrow X-ray absorption features from the low-mass X-ray binary GX13+1 with XMM-Newton
We report the detection of a complex of narrow X-ray absorption features from the low-mass X-ray binary GX13+1 during 3 XMM-Newton observations in 2000 March and April. The features are consistent with being due to resonant scattering of the K_alpha and K_beta lines of He- and H-like iron (Fe xxv and Fe xxvi) and H-like calcium (Ca xx) K_alpha. Only the Fe xxvi K_alpha line has been previously observed from GX13+1. Due to the closeness in energy the Fe xxv and Fe xxvi K_beta features may also be ascribed to Nixxvii and Nixxviii K_alpha, respectively. We also find evidence for the presence of a deep (tau~0.2) Fe xxv absorption edge at 8.83 keV. The equivalent widths of the lines do not show any obvious variation on a timescale of a few days suggesting that the absorbing material is a stable feature of the system and present during a range of orbital phases
Statistical evaluation of the flux cross-calibration of the XMM-Newton EPIC cameras
The second XMM-Newton serendipitous source catalogue, 2XMM, provides the
ideal data base for performing a statistical evaluation of the flux
cross-calibration of the XMM-Newton European Photon Imaging Cameras (EPIC). We
aim to evaluate the status of the relative flux calibration of the EPIC cameras
on board XMM-Newton (MOS1, MOS2, and pn) and investigate the dependence of the
calibration on energy, position in the field of view of the X-ray detectors,
and lifetime of the mission. We compiled the distribution of flux percentage
differences for large samples of 'good quality' objects detected with at least
two of the EPIC cameras. The mean offset of the fluxes and dispersion of the
distributions was then found by Gaussian fitting. Count rate to flux conversion
was performed with a fixed spectral model. The impact on the results of varying
this model was investigated. Excellent agreement was found between the two EPIC
MOS cameras to better than 4% from 0.2 keV to 12.0 keV. MOS cameras register
7-9% higher flux than pn below 4.5 keV and 10-13% flux excess above 4.5 keV. No
evolution of the flux ratios is seen with time, except at energies below 0.5
keV, where we found a strong decrease in the MOS to pn flux ratio with time.
This effect is known to be due to a gradually degrading MOS redistribution
function. The flux ratios show some dependence on distance from the optical
axis in the sense that the MOS to pn flux excess increases with off-axis angle.
Furthermore, in the 4.5-12.0 keV band there is a strong dependence of the MOS
to pn excess flux on the azimuthal-angle. These results strongly suggest that
the calibration of the Reflection Grating Array (RGA) blocking factors is
incorrect at high energies. Finally, we recommend ways to improve the
calculation of fluxes in future versions of XMM-Newton source catalogues.Comment: 11 pages, 10 figures, 3 tables. Abridged Abstract. Accepted for
publication in Astronomy and Astrophysic
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