16,270 research outputs found
XMM-Newton Slew Survey observations of the gravitational wave event GW150914
The detection of the first gravitational wave (GW) transient GW150914
prompted an extensive campaign of follow-up observations at all wavelengths.
Although no dedicated XMM-Newton observations have been performed, the
satellite passed through the GW150914 error box during normal operations. Here
we report the analysis of the data taken during these satellite slews performed
two hours and two weeks after the GW event. Our data cover 1.1 square degrees
and 4.8 square degrees of the final GW localization region. No credible X-ray
counterpart to GW150914 is found down to a sensitivity of 6E-13 erg/cm2/s in
the 0.2-2 keV band. Nevertheless, these observations show the great potential
of XMM-Newton slew observations for the search of the electromagnetic
counterparts of GW events. A series of adjacent slews performed in response to
a GW trigger would take <1.5 days to cover most of the typical GW credible
region. We discuss this scenario and its prospects for detecting the X-ray
counterpart of future GW detections.Comment: 6 pages, 3 figures, 2 tables. Accepted for publication in ApJ Letter
Development and verification of design methods for ducts in a space nuclear shield
A practical method for computing the effectiveness of a space nuclear shield perforated by small tubing and cavities is reported. Performed calculations use solutions for a two dimensional transport code and evaluate perturbations of that solution using last flight estimates and other kernel integration techniques. In general, perturbations are viewed as a change in source strength of scattered radiation and a change in attenuation properties of the region
Mathematical wind profiles
Augmented Fourier polynomials for mathematical representation of vertical profiles for horizontal wind velocitie
Mathematical wind profiles, parts 1, 2, 3, 4
Fourier holograph representation of wind velocity over Cape Kenned
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
Tunneling spectroscopy studies of aluminum oxide tunnel barrier layers
We report scanning tunneling microscopy and ballistic electron emission
microscopy studies of the electronic states of the uncovered and
chemisorbed-oxygen covered surface of AlOx tunnel barrier layers. These states
change when chemisorbed oxygen ions are moved into the oxide by either flood
gun electron bombardment or by thermal annealing. The former, if sufficiently
energetic, results in locally well defined conduction band onsets at ~1 V,
while the latter results in a progressively higher local conduction band onset,
exceeding 2.3 V for 500 and 600 C thermal anneals
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
Prospects for the Standard Model Higgs Boson Search in the LEP 2000 Run
A study has been performed of the discovery and exclusion potential of LEP expected in 2000 for the Higgs bosonpredicted by the Standard Model. The tradeoff factors betweenincreasing the luminosity at GeV and reduced integrated luminosity at GeVwere studied. It was shown that only in case some evidencefor a signal is observed it might be worth to increase the integratedluminosity at the lower center-of-mass energy, otherwise,LEP should aim at the highest possible center-of-mass energy.The ultimate expected exclusion limit (at the 95\%\ confidence level)of LEP (with GeV) is estimated to be 114 GeV
Chandra Observations of "The Antennae" Galaxies (NGC 4038/39)
We report the results of a deep Chandra ACIS pointing at the merging system
NGC 4038/39. We detect an extraordinarily luminous population of X-ray sources,
with luminosity well above that of XRBs in M31 and the Milky Way. If these
sources are unbeamed XRBs, our observations may point to them being 10-100Mo
black hole counterparts. We detect an X-ray bright hot ISM, with features
including bright superbubbles associated with the actively star-forming knots,
regions where hot and warm (H) ISM intermingle, and a large-scale
outflow.Comment: 7 pages, 10 figures, Accepted for publication in Ap
Near-field interaction between domain walls in adjacent Permalloy nanowires
The magnetostatic interaction between two oppositely charged transverse
domain walls (DWs)in adjacent Permalloy nanowires is experimentally
demonstrated. The dependence of the pinning strength on wire separation is
investigated for distances between 13 and 125 nm, and depinning fields up to 93
Oe are measured. The results can be described fully by considering the
interaction between the full complex distribution of magnetic charge within
rigid, isolated DWs. This suggests the DW internal structure is not appreciably
disturbed by the pinning potential, and that they remain rigid although the
pinning strength is significant. This work demonstrates the possibility of
non-contact DW trapping without DW perturbation and full continuous flexibility
of the pinning potential type and strength. The consequence of the interaction
on DW based data storage schemes is evaluated.Comment: 4 pages, 4 figures, 1 page supplimentary material (supporting.ps
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