605 research outputs found
High-Resolution spectroscopy of the low-mass X-ray binary EXO 0748-67
We present initial results from observations of the low-mass X-ray binary EXO
0748-67 with the Reflection Grating Spectrometer on board the XMM-Newton
Observatory. The spectra exhibit discrete structure due to absorption and
emission from ionized neon, oxygen, and nitrogen. We use the quantitative
constraints imposed by the spectral features to develop an empirical model of
the circumsource material. This consists of a thickened accretion disk with
emission and absorption in the plasma orbiting high above the binary plane.
This model presents challenges to current theories of accretion in X-ray binary
systems.Comment: 5 pages, 4 figures, accepted by A&A letters, XMM special issu
A New Comprehensive 2-D Model of the Point Spread Functions of the XMM-Newton EPIC Telescopes : Spurious Source Suppression and Improved Positional Accuracy
We describe here a new full 2-D parameterization of the PSFs of the three
XMM-Newton EPIC telescopes as a function of instrument, energy, off-axis angle
and azimuthal angle, covering the whole field-of-view of the three EPIC
detectors. It models the general PSF envelopes, the primary and secondary
spokes, their radial dependencies, and the large-scale azimuthal variations.
This PSF model has been constructed via the stacking and centering of a large
number of bright, but not significantly piled-up point sources from the full
field-of-view of each EPIC detector, and azimuthally filtering the resultant
PSF envelopes to form the spoke structures and the gross azimuthal shapes
observed. This PSF model is available for use within the XMM-Newton Science
Analysis System via the usage of Current Calibration Files XRTi_XPSF_0011.CCF
and later versions. Initial source-searching tests showed substantial
reductions in the numbers of spurious sources being detected in the wings of
bright point sources. Furthermore, we have uncovered a systematic error in the
previous PSF system, affecting the entire mission to date, whereby returned
source RA and Dec values are seen to vary sinusoidally about the true position
(amplitude ~0.8") with source azimuthal position. The new PSF system is now
available and is seen as a major improvement with regard to the detection of
spurious sources. The new PSF also largely removes the discovered astrometry
error and is seen to improve the positional accuracy of EPIC. The modular
nature of the PSF system allows for further refinements in the future.Comment: Accepted for publication in A&A. 15 pages, 13 figures (some of
reduced quality). A full-resolution version is available at
http://www.star.le.ac.uk/~amr30/amr_PSFpaper.pd
XMM-Newton Reflection Grating Spectrometer Observations of the Prototypical Starburst Galaxy M82
We present results from XMM-Newton Reflection Grating Spectrometer
observations of the prototypical starburst galaxy M82. These high resolution
spectra represent the best X-ray spectra to date of a starburst galaxy. A
complex array of lines from species over a wide range of temperatures is seen,
the most prominent being due to Lyman-alpha emission from abundant low Z
elements such as N, O, Ne, Mg and Si. Emission lines from Helium-like charge
states of the same elements are also seen in emission, as are strong lines from
the entire Fe-L series. Further, the OVII line complex is resolved and is seen
to be consistent with gas in collisional ionization equilibrium. Spectral
fitting indicates emission from a large mass of gas with a differential
emission measure over a range of temperatures (from 0.2 keV to 1.6 keV, peaking
at 0.7 keV), and evidence for super-solar abundances of several elements is
indicated. Spatial analysis of the data indicates that low energy emission is
more extended to the south and east of the nucleus than to the north and west.
Higher energy emission is far more centrally concentrated.Comment: 5 pages, 4 figures, MNRAS accepte
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