328 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
The interstellar oxygen-K absorption edge as observed by XMM-Newton
High resolution X-ray spectra of the Reflection Grating Spectrometer (RGS) on
board the XMM satellite are used to resolve the oxygen K absorption edge. By
combining spectra of low and high extinction sources, the observed absorption
edge can be split in the true interstellar (ISM) extinction and the
instrumental absorption. The detailed ISM edge structure closely follows the
edge structure of neutral oxygen as derived by theoretical R-matrix
calculations. However, the position of the theoretical edge requires a
wavelength shift. In addition the detailed instrumental RGS absorption edge
structure is presented. All results are verified by comparing to a subset of
Chandra LETG-HRC observations.Comment: LaTeX2e A&A style, 10 pages, 12 postscript figures, accepted for
publication in Astronomy and Astrophysic
The elemental abundances in the intracluster medium as observed with XMM-Newton
XMM-Newton observations of 19 galaxy clusters are used to measure the
elemental abundances and their spatial distributions in the intracluster
medium. The sample mainly consists of X-ray bright and relaxed clusters with a
cD galaxy. Along with detailed Si, S and Fe radial abundance distributions
within 300-700 kpc in radius, the O abundances are accurately derived in the
central region of the clusters. The Fe abundance maxima towards the cluster
center, possibly due to the metals from the cD galaxy,are spatially resolved.
The Si and S abundances also exhibit central increases in general, resulting in
uniform Fe-Si-S ratios within the cluster. In contrast, the O abundances are in
general uniform over the cluster. The mean O to Fe ratio within the cluster
core is sub-solar, while that of the cluster scale is larger than the solar
ratio. These measurements indicate that most of the Fe-Si-S and O in the
intracluster medium have different origins, presumably in supernovae Ia and II,
respectively. The obtained Fe and O mass are also used to discuss the past star
formation history in clusters.Comment: Accepted for publication in Astronomy and Astrophysic
Hyper-velocity impact test and simulation of a double-wall shield concept for the Wide Field Monitor aboard LOFT
The space mission LOFT (Large Observatory For X-ray Timing) was selected in
2011 by ESA as one of the candidates for the M3 launch opportunity. LOFT is
equipped with two instruments, the Large Area Detector (LAD) and the Wide Field
Monitor (WFM), based on Silicon Drift Detectors (SDDs). In orbit, they would be
exposed to hyper-velocity impacts by environmental dust particles, which might
alter the surface properties of the SDDs. In order to assess the risk posed by
these events, we performed simulations in ESABASE2 and laboratory tests. Tests
on SDD prototypes aimed at verifying to what extent the structural damages
produced by impacts affect the SDD functionality have been performed at the Van
de Graaff dust accelerator at the Max Planck Institute for Nuclear Physics
(MPIK) in Heidelberg. For the WFM, where we expect a rate of risky impacts
notably higher than for the LAD, we designed, simulated and successfully tested
at the plasma accelerator at the Technical University in Munich (TUM) a
double-wall shielding configuration based on thin foils of Kapton and
Polypropylene. In this paper we summarize all the assessment, focussing on the
experimental test campaign at TUM.Comment: Proc. SPIE 9144, Space Telescopes and Instrumentation 2014:
Ultraviolet to Gamma Ray, 91446
First Light Measurements with the XMM-Newton Reflection Grating Spectrometers: Evidence for an Inverse First Ionisation Potential Effect and Anomalous Ne A bundance in the Coronae of HR 1099
The RS CVn binary system HR 1099 was extensively observed by the XMM-Newton
observatory in February 2000 as its first-light target. A total of 570 ks of
exposure time was accumulated with the Reflection Grating Spectrometers (RGS).
The integrated X-ray spectrum between 5-35 Angstrom is of unprecedented quality
and shows numerous features attributed to transitions of the elements C, N, O,
Ne, Mg, Si, S, Fe, and Ni. We perform an in-depth study of the elemental
composition of the average corona of this system, and find that the elemental
abundances strongly depend on the first ionisation potential (FIP) of the
elements. But different from the solar coronal case, we find an inverse FIP
effect, i.e., the abundances (relative to oxygen) increase with increasing FIP.
Possible scenarios, e.g., selective enrichment due to Ne-rich flare-like
events, are discussed.Comment: 5 pages, 4 figures. Accepted by A&A Letters, XMM issu
The search for decaying Dark Matter
We propose an X-ray mission called Xenia to search for decaying superweakly
interacting Dark Matter particles (super-WIMP) with a mass in the keV range.
The mission and its observation plan are capable of providing a major break
through in our understanding of the nature of Dark Matter (DM). It will
confirm, or reject, predictions of a number of particle physics models by
increasing the sensitivity of the search for decaying DM by about two orders of
magnitude through a wide-field imaging X-ray spectrometer in combination with a
dedicated observation program.
The proposed mission will provide unique limits on the mixing angle and mass
of neutral leptons, right handed partners of neutrinos, which are important
Dark Matter candidates. The existence of these particles is strongly motivated
by observed neutrino flavor oscillations and the problem of baryon asymmetry of
the Universe.
In super-WIMP models, the details of the formation of the cosmic web are
different from those of LambdaCDM. The proposed mission will, in addition to
the search for decaying Dark Matter, provide crucial insight into the nature of
DM by studying the structure of the "cosmic web". This will be done by
searching for missing baryons in emission, and by using gamma-ray bursts as
backlight to observe the warm-hot intergalactic media in absorption.Comment: A white paper submitted in response to the Fundamental Physics
Roadmap Advisory Team (FPR-AT) Call for White Paper
Spectral properties of gammaâray bursts observed by COMPTEL
During the first year of operation, the COMPTEL instrument on board the Compton Gamma Ray Observatory detected 22 Îłâray bursts within its field of view. Spectra and time histories for the strongest 7 of these bursts have been obtained from both the main instrument (0.75â30 MeV) and the burst modules (0.1â10 MeV). The deconvolved photon spectra for the majority of bursts are fit by a single power law model with spectral index between â1.6 and â2.8. One strong burst, GRB 910814, exhibited significant curvature and could not be fit by a single power law model. A broken power law model with a break in slope at âŒ2 MeV is a good fit to the time averaged spectrum of this burst. There is evidence, at the 2.8Ï level, for a change in the break energy of GRB 910814, from above 2 MeV to below 1 MeV during the first 9 s of the burst
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