7,279 research outputs found
Extended X-ray emission in the IC 2497 - Hanny's Voorwerp system: energy injection in the gas around a fading AGN
We present deep Chandra X-ray observations of the core of IC 2497, the galaxy
associated with Hanny's Voorwerp and hosting a fading AGN. We find extended
soft X-ray emission from hot gas around the low intrinsic luminosity
(unobscured) AGN ( erg s). The
temperature structure in the hot gas suggests the presence of a bubble or
cavity around the fading AGN (\mbox{E_{\rm bub}} \sim 10^{54} - 10^{55}
erg). A possible scenario is that this bubble is inflated by the fading AGN,
which after changing accretion state is now in a kinetic mode. Other
possibilities are that the bubble has been inflated by the past luminous quasar
( erg s), or that the temperature gradient is
an indication of a shock front from a superwind driven by the AGN. We discuss
the possible scenarios and the implications for the AGN-host galaxy
interaction, as well as an analogy between AGN and X-ray binaries lifecycles.
We conclude that the AGN could inject mechanical energy into the host galaxy at
the end of its lifecycle, and thus provide a source for mechanical feedback, in
a similar way as observed for X-ray binaries.Comment: 9 pages, 5 figures, accepted for publication in MNRA
Nurses\u27 Alumnae Association Bulletin - Volume 16 Number 1
Alumnae Notes
ANA Biennial Convention
Cancer of the Cervix, Uterus and Ovaries
Committee Reports
Digest of Alumnae Association Meetings
Greetings from Miss Childs
Greetings from the President
Graduation Awards - 1950
Isotopes and the Nurse - Dr. T.P. Eberhard
Marriages
Necrology
New Arrivals
Nursing Care in Heart Disease with Pulmonary Infarction
Nursing Care of a Mitral Commissurotomy
Physical Advances at Jefferson - 1950
Policies of the Private Duty Nurses\u27 Registry
Staff Activities, 1950-1951
Students\u27 Corner
The Department of Surgical Research - Drs. Templeton and Gibbon
White Haven and Barton Memorial Division
HD148937: a multiwavelength study of the third Galactic member of the Of?p class
Three Galactic O-type stars belong to the rare class of Of?p objects: HD108,
HD191612, and HD148937. The first two stars show a wealth of phenomena,
including magnetic fields and strong X-ray emission, light variability, and
dramatic periodic spectral variability. We present here the first detailed
optical and X-ray study of the third Galactic Of?p star, HD148937.
Spectroscopic monitoring has revealed low-level variability in the Balmer and
HeII4686 lines, but constancy at HeI and CIII4650. The Ha line exhibits profile
variations at a possible periodicity of ~7d. Model atmosphere fits yield
T_{eff}=41000+-2000K, log(g)=4.0+-0.1, Mdot_{sph}<~ 10^{-7}Msol/yr and a
surabondance of nitrogen by a factor of four. At X-ray wavelengths, HD148937
resembles HD108 and HD191612 in having a thermal spectrum dominated by a
relatively cool component (kT=0.2keV), broad lines (>1700km/s), and an
order-of-magnitude overluminosity compared to normal O stars (log
[L_X^unabs/L_BOL] ~ -6).Comment: accepted by AJ; 15p, 15fig available in jp
A New Algorithm for Computing Statistics of Weak Lensing by Large-Scale Structure
We describe an efficient algorithm for calculating the statistics of weak
lensing by large-scale structure based on a tiled set of independent
particle-mesh N-body simulations which telescope in resolution along the line
of sight. This efficiency allows us to predict not only the mean properties of
lensing observables such as the power spectrum, skewness and kurtosis of the
convergence, but also their sampling errors for finite fields of view, which
are themselves crucial for assessing the cosmological significance of
observations. We find that the nongaussianity of the distribution substantially
increases the sampling errors for the skewness and kurtosis in the several to
tens of arcminutes regime, whereas those for the power spectrum are only
fractionally increased even out to wavenumbers where shot noise from the
intrinsic ellipticities of the galaxies will likely dominate the errors.Comment: 12 pages, 13 figures; minor changes reflect accepted versio
Reproducibility and speed of landmarking process in cephalometric analysis using two input devices: mouse-driven cursor versus pen
To define if the new portable appliances, like smartphone, iPad, small laptop and tablet can be used in cephalometric tracing without dropping out the validity of any measurement.
METHODS:We investigated and compared the reproducibility and the speed of landmarks identification process on lateral X-rays in two input devices: a mouse-driven cursor and a pen used as input means in mobile devices. One expert located 22 landmarks on 15 lateral X-rays in a repeated measure design two times, at time T1 and T2, after at least one month. The Intraclass Correlation coefficient was used to evaluate the reproducibility for each landmark tracing and the agreement between the value derived from both input devices. Also, the mean errors in measurements, the standard deviation and the Friedman Test significans (P < 0.05) between both input were statistically evaluated.
RESULTS:All landmarks had a high agreement and the Friedman Test indicated statistically significant differences (P<0.05) for the identification of Na, Po, Pt, PNS, Ba, Pg, Gn, UIE, UIA, APOcc and PPOcc landmarks.
CONCLUSIONS:Even if the mouse input give higher agreement for landmark tracing the differences are really minimal and they can be ignored in private practice. We suggest the adequacy of pen input in clinical setting
Effects of a deformation of a star on the gravitational lensing
We study analytically a gravitational lens due to a deformed star, which is
modeled by using a monopole and a quadrupole moment. Positions of the images
are discussed for a source on the principal axis. We present explicit
expressions for the lens equation for this gravitational lens as a single real
tenth-order algebraic equation. Furthermore, we compute an expression for the
caustics as a discriminant for the polynomial. Another simple parametric
representation of the caustics is also presented in a more tractable form. A
simple expression for the critical curves is obtained to clarify a topological
feature of the critical curves; the curves are simply connected if and only if
the distortion is sufficiently large.Comment: 8 pages; accepted for publication in MNRA
Cosmological parameters from combined second- and third-order aperture mass statistics of cosmic shear
We present predictions for cosmological parameter constraints from combined
measurements of second- and third-order statistics of cosmic shear. We define
the generalized third-order aperture mass statistics and show that it
contains much more information about the bispectrum of the projected matter
density than the skewness of the aperture mass. From theoretical models as well
as from LCDM ray-tracing simulations, we calculate and and
their dependence on cosmological parameters. The covariances including shot
noise and cosmic variance of M_ap^2, M_ap^3 and their cross-correlation are
calculated using ray-tracing simulations. We perform an extensive Fisher matrix
analysis, and for various combinations of cosmological parameters, we predict
1-sigma-errors corresponding to measurements from a deep 29 square degree
cosmic shear survey. Although the parameter degeneracies can not be lifted
completely, the (linear) combination of second- and third-order aperture mass
statistics reduces the errors significantly. The strong degeneracy between
Omega_m and sigma_8, present for all second-order cosmic shear measures, is
diminished substantially, whereas less improvement is found for the
near-degenerate pair consisting of the shape parameter Gamma and the spectral
index n_s. Uncertainties in the source galaxy redshift z_0 increase the errors
of all other parameters.Comment: Revised version, 15 pages, 10 figures, in press at A&A. Some changes
were made including an extension of the analysis. Matches the published
versio
Evolution of the magnetic field in magnetars
We use numerical MHD to look at the stability of a possible poloidal field in
neutron stars (Flowers & Ruderman 1977), and follow its unstable evolution,
which leads to the complete decay of the field. We then model a neutron star
after the formation of a solid crust of high conductivity. As the initial
magnetic field we use the stable `twisted torus' field which was the result of
our earlier work (Braithwaite & Nordlund 2005), since this field is likely to
exist in the interior of the star at the time of crust formation. We follow the
evolution of the field under the influence of diffusion, and find that large
stresses build up in the crust, which will presumably lead to cracking. We put
this forward as a model for outbursts in soft gamma repeaters.Comment: 11 pages, 12 figures, submitted to A&
The ROSAT-ESO Flux-Limited X-Ray (REFLEX) Galaxy Cluster Survey VI: Constraints on the cosmic matter density from the KL power spectrum
The Karhunen-Lo\'{e}ve (KL) eigenvectors and eigenvalues of the sample
correlation matrix are used to analyse the spatial fluctuations of the REFLEX
clusters of galaxies. The method avoids the disturbing effects of correlated
power spectral densities which affects all previous cluster measurements on Gpc
scales. Comprehensive tests use a large set of independent REFLEX-like mock
cluster samples extracted from the Hubble Volume Simulation. It is found that
unbiased measurements on Gpc scales are possible with the REFLEX data. The
distribution of the KL eigenvalues are consistent with a Gaussian random field
on the 93.4% confidence level. Assuming spatially flat cold dark matter models,
the marginalization of the likelihood contours over different sample volumes,
fiducial cosmologies, mass/X-ray luminosity relations and baryon densities,
yields the 95.4% confidence interval for the matter density of
. The N-body simulations show that cosmic variance,
although difficult to estimate, is expected to increase the confidence
intervals by about 50%.Comment: 11 pages, 7 figures, accepted for publication in MNRA
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