44,354 research outputs found
Magnetoelectric properties of [FeCl(HO)] with K, Rb, Cs
The compounds [FeCl(HO)] with K, Rb, Cs are identified as
new linear magnetoelectric materials. We present a detailed investigation of
their linear magnetoelectric properties by measurements of pyroelectric
currents, dielectric constants and magnetization. The anisotropy of the linear
magnetoelectric effect of the K-based and Rb-based compound is consistent with
the magnetic point group , already reported in literature. A symmetry
analysis of the magnetoelectric effect of the Cs-based compound allows to
determine the magnetic point group and to develop a model for its
magnetic structure. In addition, magnetic-field versus temperature phase
diagrams are derived and compared to the closely related multiferroic
(NH)[FeCl(HO)].Comment: 17 pages, 10 figures (updated to the weakly revised version that has
been accepted for publication
t-SURFF: Fully Differential Two-Electron Photo-Emission Spectra
The time dependent surface flux (t-SURFF) method is extended to single and
double ionization of two electron systems. Fully differential double emission
spectra by strong pulses at extreme UV and infrared wave length are calculated
using simulation volumes that only accommodate the effective range of the
atomic binding potential and the quiver radius of free electrons in the
external field. For a model system we find pronounced dependence of shake-up
and non-sequential double ionization on phase and duration of the laser pulse.
Extension to fully three-dimensional calculations is discussed
The 2-10 keV emission properties of PSR B1937+21
We present the results of a BeppoSAX observation of the fastest pulsar known:
PSR B1937+21. The ~ 200 ks observation (78.5 (34) ks MECS (LECS) exposure
times) allowed us to investigate with high statistical significance both the
spectral properties and the pulse profile shape. The absorbed power law
spectral model gave a photon index of ~ 1.7 and N_H ~ 2.3 x 10^22 cm^-2. These
values explain both a) the ROSAT non-detection and b) the deviant estimate of a
photon index of ~ 0.8 obtained by ASCA. The pulse profile appears, for the
first time, clearly double peaked with the main component much stronger than
the other. The statistical significance is 10 sigma (main peak) and 5 sigma
(secondary peak). The 1.6-10 keV pulsed fraction is consistent with 100%; only
in the 1.6-4 keV band there is a ~ 2 sigma indication for a DC component. The
secondary peak is detected significantly only for energies above 3 / 4 keV. The
unabsorbed (2-10 keV) flux is F_2-10 = 3.7 x 10^-13 erg cm^-2 s^-1, implying a
luminosity of L_X = 4.6 x 10^31 Theta (d/3.6 kpc)^2 erg s^-1 and an X-ray
efficiency of eta = 4 x 10^-5 Theta, where Theta is the solid angle spanned by
the emission beam. These results are in agreement with those obtained by ASCA.Comment: 4 pages, 4 figures, 2 tables. To appear in the Proceedings of the
270. WE-Heraeus Seminar on Neutron Stars, Pulsars and Supernova Remnants,
Jan. 21-25, 2002, Physikzentrum Bad Honnef, eds W. Becker, H. Lesch & J.
Truemper. Proceedings are available as MPE-Report 27
Explaining Jupiter's magnetic field and equatorial jet dynamics
Spacecraft data reveal a very Earth-like Jovian magnetic field. This is
surprising since numerical simulations have shown that the vastly different
interiors of terrestrial and gas planets can strongly affect the internal
dynamo process. Here we present the first numerical dynamo that manages to
match the structure and strength of the observed magnetic field by embracing
the newest models for Jupiter's interior. Simulated dynamo action primarily
occurs in the deep high electrical conductivity region while zonal flows are
dynamically constrained to a strong equatorial jet in the outer envelope of low
conductivity. Our model reproduces the structure and strength of the observed
global magnetic field and predicts that secondary dynamo action associated to
the equatorial jet produces banded magnetic features likely observable by the
Juno mission. Secular variation in our model scales to about 2000 nT per year
and should also be observable during the one year nominal mission duration.Comment: 7 pages, 4 figures, accepted for publication in Geophysical Research
Letter
Integral field spectroscopy of QSO host galaxies
We describe a project to study the state of the ISM in ~20 low redshift
(z<0.3) QSO host galaxies observed with the PMAS integral field spectrograph.
We describe method developement to access the stellar and gas component of the
spectrum without the strong nuclear emission to access the host galaxy
properties also in the central region. It shows that integral field
spectroscopy promises to be very efficient to study the gas distribution and
its velocity field, and also spatially resolved stellar population in the host
galaxies also of luminous AGN.Comment: 4 pages, 6 figures, Euro3D Science Workshop, Cambridge, May 2003, AN,
accepte
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