18,611 research outputs found
Tool for use in lifting pin supported objects
A tool for use in lifting a pin-supported, electronic package mounted in juxtaposition with the surface of an electronic circuit board is described. The tool is configured to be received beneath a pin-supported package and is characterized by a manually operable linkage, including an elongated, rigid link is supported for axial reciprocation and a pivotal link pinned to the body and supported for oscillation induced in response to axial motion imparted to the rigid link. A lifting plate is pivotally coupled to the distal end of the pivotal link so that oscillatory motion imparted to the pivotal link serves to move the plate vertically for elevating the plate into lifting engagement with the electronic package positioned thereabove
Cross-Calibration of the XMM-Newton EPIC pn & MOS On-Axis Effective Areas Using 2XMM Sources
We aim to examine the relative cross-calibration accuracy of the on-axis
effective areas of the XMM-Newton EPIC pn and MOS instruments. Spectra from a
sample of 46 bright, high-count, non-piled-up isolated on-axis point sources
are stacked together, and model residuals are examined to characterize the EPIC
MOS-to-pn inter-calibration. The MOS1-to-pn and MOS2-to-pn results are broadly
very similar. The cameras show the closest agreement below 1 keV, with MOS
excesses over pn of 0-2% (MOS1/pn) and 0-3% (MOS2/pn). Above 3 keV, the MOS/pn
ratio is consistent with energy-independent (or only mildly increasing)
excesses of 7-8% (MOS1/pn) and 5-8% (MOS2/pn). In addition, between 1-2 keV
there is a `silicon bump' - an enhancement at a level of 2-4% (MOS1/pn) and
3-5% (MOS2/pn). Tests suggest that the methods employed here are stable and
robust. The results presented here provide the most accurate cross-calibration
of the effective areas of the XMM-Newton EPIC pn and MOS instruments to date.
They suggest areas of further research where causes of the MOS-to-pn
differences might be found, and allow the potential for corrections to and
possible rectification of the EPIC cameras to be made in the future.Comment: 8 Pages, 2 figures (3 panels), 1 table. Accepted for publication in
A&
The XMM-Newton slew survey in the 2-10 keV band
The XMM-Newton Slew Survey (XSS) covers a significant fraction of the sky in
a broad X-ray bandpass. Although shallow by contemporary standards, in the
`classical' 2-10 keV band of X-ray astronomy, the XSS provides significantly
better sensitivity than any currently available all-sky survey. We investigate
the source content of the XSS, focussing on detections in the 2-10 keV band
down to a very low threshold (> 4 counts net of background). At the faint end,
the survey reaches a flux sensitivity of roughly 3e-12 erg/cm2/s (2-10 keV).
Our starting point was a sample of 487 sources detected in the XMMSL1d2 XSS at
high galactic latitude in the hard band. Through cross-correlation with
published source catalogues from surveys spanning the electromagnetic spectrum
from radio to gamma-rays, we find that 45% of the sources have likely
identifications with normal/active galaxies, 18% are associated with other
classes of X-ray object (nearby coronally active stars, accreting binaries,
clusters of galaxies), leaving 37% of the XSS sources with no current
identification. We go on to define an XSS extragalactic hard band sample
comprised of 219 galaxies and active galaxies. We investigate the properties of
this extragalactic sample including its X-ray logN-logS distribution. We find
that in the low-count limit, the XSS is strongly affected by Eddington bias.
There is also a very strong bias in the XSS against the detection of extended
sources, most notably clusters of galaxies. A significant fraction of the
detections at and around the low-count limit may be spurious. Nevertheless, it
is possible to use the XSS to extract a reasonably robust sample of
extragalactic sources, excluding galaxy clusters. The differential logN-logS
relation of these extragalactic sources matches very well to the HEAO-1 A2
all-sky survey measurements at bright fluxes and to the 2XMM source counts at
the faint end.Comment: 16 pages, 13 figures, FITS table of XSS extragalactic sample
available from http://www.star.le.ac.uk/~amr30/Slew
Potential solar axion signatures in X-ray observations with the XMM-Newton observatory
The soft X-ray flux produced by solar axions in the Earth's magnetic field is
evaluated in the context of ESA's XMM-Newton observatory. Recent calculations
of the scattering of axion-conversion X-rays suggest that the sunward
magnetosphere could be an observable source of 0.2-10 keV photons. For
XMM-Newton, any conversion X-ray intensity will be seasonally modulated by
virtue of the changing visibility of the sunward magnetic field region. A
simple model of the geomagnetic field is combined with the ephemeris of
XMM-Newton to predict the seasonal variation of the conversion X-ray intensity.
This model is compared with stacked XMM-Newton blank sky datasets from which
point sources have been systematically removed. Remarkably, a seasonally
varying X-ray background signal is observed. The EPIC count rates are in the
ratio of their X-ray grasps, indicating a non-instrumental, external photon
origin, with significances of 11(pn), 4(MOS1) and 5(MOS2) sigma. After
examining the constituent observations spatially, temporally and in terms of
the cosmic X-ray background, we conclude that this variable signal is
consistent with the conversion of solar axions in the Earth's magnetic field.
The spectrum is consistent with a solar axion spectrum dominated by
bremsstrahlung- and Compton-like processes, i.e. axion-electron coupling
dominates over axion-photon coupling and the peak of the axion spectrum is
below 1 keV. A value of 2.2e-22 /GeV is derived for the product of the
axion-photon and axion-electron coupling constants, for an axion mass in the
micro-eV range. Comparisons with limits derived from white dwarf cooling may
not be applicable, as these refer to axions in the 0.01 eV range. Preliminary
results are given of a search for axion-conversion X-ray lines, in particular
the predicted features due to silicon, sulphur and iron in the solar core, and
the 14.4 keV transition line from 57Fe.Comment: Accepted for publication in MNRAS. 67 pages total, including 39
figures, 6 table
The XMM-Newton Slew Survey: Towards The Whole X-ray Sky and the Rarest X-ray Events
The data collected by XMM-Newton as it slews between pointings currently
cover almost half the entire sky, and many familiar features and new sources
are visible. The soft-band sensitivity limit of the Slew is close to that of
the RASS, and a large-area Slew-RASS comparison now provides the best
opportunity for discovering extremely rare high-variability objects.Comment: To appear in Proceedings of "X-ray Astronomy 2009: Present Status,
Multi-Wavelength Approach and Future Perspectives", Bologna, Italy, September
7-11, 2009, AIP, eds. A. Comastri, M. Cappi, and L. Angelin
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
Vortex lattices in the lowest Landau level for confined Bose-Einstein condensates
We present the results of numerical calculations of the groundstates of
weakly-interacting Bose-Einstein condensates containing large numbers of
vortices. Our calculations show that these groundstates appear to be close to
uniform triangular vortex lattices. However, slight deviations from a uniform
triangular lattice have dramatic consequences on the overall particle
distribution. In particular, we demonstrate that the overall particle
distribution averaged on a lengthscale large compared to the vortex lattice
constant is well approximated by a Thomas-Fermi profile.Comment: 5 pages, 4 figure
Gapless Spin-Fluid Ground State in a Random Quantum Heisenberg Magnet
We examine the spin- quantum Heisenberg magnet with Gaussian-random,
infinite-range exchange interactions. The quantum-disordered phase is accessed
by generalizing to symmetry and studying the large limit. For large
the ground state is a spin-glass, while quantum fluctuations produce a
spin-fluid state for small . The spin-fluid phase is found to be generically
gapless - the average, zero temperature, local dynamic spin-susceptibility
obeys \bar{\chi} (\omega ) \sim \log(1/|\omega|) + i (\pi/2) \mbox{sgn}
(\omega) at low frequencies. This form is identical to the phenomenological
`marginal' spectrum proposed by Varma {\em et. al.\/} for the doped cuprates.Comment: 13 pages, REVTEX, 2 figures available by request from
[email protected]
Low-power radio galaxy environments in the Subaru/XMM-Newton Deep Field at z~0.5
We present multi-object spectroscopy of galaxies in the immediate (Mpc-scale)
environments of four low-power (L_1.4 GHz < 10^25 W/Hz) radio galaxies at
z~0.5, selected from the Subaru/XMM-Newton Deep Field. We use the spectra to
calculate velocity dispersions and central redshifts of the groups the radio
galaxies inhabit, and combined with XMM-Newton (0.3-10 keV) X-ray observations
investigate the L_X--sigma_v and T_X--sigma_v scaling relationships. All the
radio galaxies reside in moderately rich groups -- intermediate environments
between poor groups and rich clusters, with remarkably similar X-ray
properties. We concentrate our discussion on our best statistical example that
we interpret as a low-power (FRI) source triggered within a sub-group, which in
turn is interacting with a nearby group of galaxies, containing the bulk of the
X-ray emission for the system -- a basic scenario which can be compared to more
powerful radio sources at both high (z>4) and low (z<0.1) redshifts. This
suggests that galaxy-galaxy interactions triggered by group mergers may play an
important role in the life-cycle of radio galaxies at all epochs and
luminosities.Comment: 12 pages, 7 figures, accepted for publication in MNRAS. High
resolution version available upon reques
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