publicationDate stringlengths 1 2.79k | title stringlengths 1 36.5k ⌀ | abstract stringlengths 1 37.3k ⌀ | id stringlengths 9 47 |
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2003-03-04 | Preparation of enriched cosmic ray mass groups with KASCADE | The KASCADE experiment measures a high number of EAS observables with a large
degree of sampling of the electron-photon, muon, and hadron components. It
provides accurate data for an event-by-event analysis of the primary cosmic ray
flux in the energy range around the knee. The possibility of selecting samples
of enric... | 0303070v1 |
2003-05-21 | Ratio of color and effective temperatures in X-ray burst spectra | We present model atmospheres and theoretical spectra for X-ray bursters. Our
models include the effects of Compton scattering on free electrons. The
atmospheres have compositions that are mixtures of hydrogen, helium, and iron.
For our models the ratio of color temperature, $T_c$, to effective temperature,
$T_{eff}$, i... | 0305391v1 |
2003-08-29 | The Iron Abundance and Density Structure of the Inner Ring around SN 1987A | We present a spectroscopic study of the inner circumstellar ring around SN
1987A. The aim is to determine the elemental abundances and density structure,
with particular emphasis on the abundance of iron. We acquired and analysed
optical spectra at the Anglo-Australian Telescope (AAT) between 1400 and 4300
days post-ex... | 0308533v1 |
2003-09-16 | The hard X-ray spectrum of the Seyfert galaxy IRAS 18325-5926: cool corona, reflection from an ionized disk and variable iron K emission | We report our analysis of X-ray spectra of the Seyfert galaxy IRAS 18325-5926
(=Fairall 49) obtained from various X-ray observatories prior to XMM-Newton,
including new results from two RXTE and one BeppoSAX observations. A relatively
steep continuum slope (photon-index of ~2.2) in the 2-15 keV band is confirmed.
The c... | 0309432v1 |
2003-09-17 | A new Method to Constrain the Iron Abundance from Cooling Delays in Coronal Loops | Recent observations with TRACE reveal that the time delay between the
appearance of a cooling loop in different EUV temperature filters is
proportional to the loop length, dt_12 ~ L. We model this cooling delay in
terms of radiative loss and confirm this linear relationship theoretically. We
derive an expression that c... | 0309506v1 |
2003-10-17 | The high energy emission line spectrum of NGC 1068 | We present and discuss the high energy (E>4 keV) XMM-Newton spectrum of the
Seyfert 2 galaxy, NGC 1068. Possible evidence for flux variability in both the
neutral and ionized reflectors with respect to a BeppoSAX observation taken 3.5
years before is found. Several Fe and Ni emission lines, from both neutral and
highly... | 0310492v1 |
2003-10-27 | Constraints on SN Ia Progenitors and ICM enrichment from field and cluster SN rates | The iron mass in galaxy clusters is about 6 times larger than could have been
produced by core-collapse SNe, assuming the stars in cluster galaxies formed
with a standard IMF. Type-Ia SNe have been proposed as the alternative dominant
iron source. We use our HST measurements of the cluster SN-Ia rate at high
redshift t... | 0310768v1 |
2004-02-04 | Relativistic Iron Lines in Galactic Black Holes: Recent Results and Lines in the ASCA Archive | Recent observations with Chandra and XMM-Newton, aided by broad-band spectral
coverage from RXTE, have revealed skewed relativistic iron emission lines in
stellar-mass Galactic black hole systems. Such systems are excellent
laboratories for testing General Relativity, and relativistic iron lines
provide an important to... | 0402101v1 |
2004-04-08 | Iron Line Spectroscopy of NGC4593 with XMM-Newton: Where is the Black Hole Accretion Disk? | We present an analysis of the 2-10keV XMM-Newton/EPIC-pn spectrum of the
Seyfert-1 galaxy NGC4593. Apart from the presence of two narrow emission lines
corresponding to the Kalpha lines of cold and hydrogen-like iron, this spectrum
possesses a power-law form to within 3-5%. There is a marked lack of spectral
features f... | 0404187v1 |
2004-06-28 | Iron Abundance Diagnostics in High-Redshift QSOs | The abundance of alpha-process elements such as magnesium and carbon relative
to iron measured from the broad emission lines of QSOs can serve as a
diagnostic of the star formation and chemical enrichment histories of their
host galaxies.
We investigate the relationship between Fe/Mg and Fe/C abundance ratios and
the... | 0406630v1 |
2004-07-07 | The Additional Line Component within the Iron KαProfile in MCG-6-30-15: Evidence for Blob Ejection? | The EPIC data of MCG -6-30-15 observed by XMM-Newton were analyzed for the
complexities of the iron K-alpha line. Here we report that the additional line
component (ALC) at 6.9 keV undoubtedly appears within the broad iron Kalpha;
line profile at the high state, whereas it disappears at the low state. These
state-depen... | 0407124v1 |
2004-09-08 | Atomic data from the Iron Project.LVIII. New radiative transition probabilities for Fe IV including fine structure | We present new calculations for transition probabilities of Fe IV, with much
more extensive datasets than heretofore available. The large-scale close
coupling R-matrix calculations yield 1,798 LS bound states with n $\leq$ 11 and
$l \leq$ 9, and corresponding transition probabilities for 138,121 dipole
allowed transiti... | 0409202v1 |
2004-11-01 | The absorption spectrum of V838 Mon in 2002 February - March. I. Atmospheric parameters and iron abundance | We present a determination of the effective temperatures, iron abundances,
and microturbulent velocities for the pseudophotosphere of V838 Mon on 2002
February 25, and March 2 and 26. Physical parameters of the line forming region
were obtained in the framework of a self-consistent approach, using fits of
synthetic spe... | 0411032v1 |
2004-11-22 | Fe XXV and Fe XXVI lines from low velocity, photoionised gas in the X-ray spectra of AGN | We have calculated the equivalent widths of the absorption lines produced by
Fe XXV and Fe XXVI in a Compton-thin, low-velocity photoionised material
illuminated by the nuclear continuum in AGN. The results, plotted against the
ionisation parameter and the column density of the gas, are a complement to
those presented ... | 0411603v1 |
2004-11-22 | The iron $K_α$ lines as a tool for magnetic field estimations in non-flat accretion flows | Observations of AGNs and microquasars by ASCA, RXTE, Chandra and XMM-Newton
indicate the existence of broad X-ray emission lines of ionized heavy elements
in their spectra. Such spectral lines were discovered also in X-ray spectra of
neutron stars and X-ray afterglows of GRBs. Recently, Zakharov et al. (MNRAS,
2003, 34... | 0411608v1 |
2004-12-09 | Broad Iron Lines in AGN and X-ray Binaries | Several AGN and black hole X-ray binaries show a clear very broad iron line
which is strong evidence that the black holes are rapidly spinning. Detailed
analysis of these objects shows that the emission line is not significantly
affected by absorption and that the source variability is principally due to
variation in a... | 0412224v2 |
2005-02-16 | A changing inner radius in the accretion disc of Q0056-363? | Q0056-363 is the most powerful X-ray quasar known to exhibit a broad, likely
relativistic iron line (Porquet & Reeves 2003). It has been observed twice by
XMM-$Newton$, three and half years apart (July 2000 and December 2003). In the
second observation, the UV and soft X-ray fluxes were fainter, the hard X-ray
power la... | 0502323v1 |
2005-09-28 | Isotopes Tell Origin and Operation of the Sun | The Iron Sun formed on the collapsed core of a supernova and now acts as a
magnetic plasma diffuser, as did the precursor star, separating ions by mass.
This process covers the solar surface with lightweight elements and with
lighter isotopes of each element. Running difference images expose rigid,
iron-rich structures... | 0510001v1 |
2005-10-18 | The Metallicity Dependence of the Cepheid Period-Luminosity Relation | We have assessed the influence of the stellar iron content on the Cepheid
Period-Luminosity (PL) relation by relating the V band residuals from the
Freedman et al (2001) PL relation to [Fe/H] for 68 Galactic and Magellanic
Cloud Cepheids. The iron abundances were measured from FEROS and UVES
high-resolution and high si... | 0510521v1 |
2005-10-21 | Resolving the Fe xxv Triplet with Chandra in Cen X-3 | We present the results of a 45 ks Chandra observation of the high-mass X-ray
binary Cen X--3 at orbital phases between 0.13 and 0.40 (in the eclipse
post-egress phases). Here we concentrate on the study of discrete features in
the energy spectrum at energies between 6 and 7 keV, i.e. on the iron
K$_\alpha$ line region,... | 0510645v1 |
2005-11-02 | The Iron K-shell features of MXB 1728-34 from a Simultaneous Chandra-RXTE Observation | We report on a simultaneous Chandra and RossiXTE observation of the low-mass
X-ray binary atoll bursting source MXB 1728-34 performed on 2002 March 3-5. We
fit the 1.2-35 keV continuum spectrum with a blackbody plus a Comptonized
component. Large residuals at 6-10 keV can be fitted by a broad (FWHM ~ 2 keV)
Gaussian em... | 0511072v1 |
2005-11-14 | A prominent relativistic iron line in the Seyfert 1 MCG-02-14-009 | I report the discovery of a prominent broad and asymmetrical feature near 6.4
keV in the Seyfert 1 MCG-02-14-009 (z=0.028) with XMM-Newton/EPIC. The present
short X-ray observation (PN net exposure time ~5 ks) is the first one above 2
keV for MCG-02-14-009. The feature can be explained by either a relativistic
iron lin... | 0511387v1 |
2005-11-16 | Oxygen and Iron Abundances in Nearby Galaxies Using Ultraluminous X-ray Sources | We determined oxygen and iron abundances of the interstellar medium (ISM)
using K-shell (O) and L-shell (Fe) X-ray photo-ionization edges towards Ultra
luminous X-ray sources (ULXs). We determine the hydrogen column densities (n_H)
towards the ULXs from XMM-Newton archival spectra of 14 ULX sources. We compare
our X-ra... | 0511493v1 |
2005-11-23 | Iron depletion in the hot bubbles in planetary nebulae | We have searched for the emission from \fex and \fexiv that is expected from
the gas emitting in diffuse X-rays in \bd, NGC 6543, NGC 7009, and NGC 7027.
Neither line was detected in any object. Models that fit the X-ray spectra of
these objects indicate that the \fex emission should be below our detection
thresholds, ... | 0511681v1 |
2006-01-12 | Permitted Oxygen Abundances and the Temperature Scale of Metal-Poor Turn-Off Stars | We use high quality VLT/UVES published data of the permitted OI triplet and
FeII lines to determine oxygen and iron abundances in unevolved (dwarfs,
turn-off, subgiants) metal-poor halo stars. The calculations have been
performed both in LTE and NLTE, employing effective temperatures obtained with
the new infrared flux... | 0601256v1 |
2006-03-02 | Abundance studies of sdB stars using UV echelle HST/STIS spectroscopy | Aims: We test the hypothesis that the pulsations in sdB stars are correlated
with the surface abundances of iron-group elements. Any correlation might
explain why, when given two spectroscopically similar stars, one will pulsate
while the other will not. Methods: We have obtained high-resolution ultraviolet
spectra two... | 0603069v1 |
2006-04-27 | A Likelihood Method for Measuring the Ultrahigh Energy Cosmic Ray Composition | Air fluorescence detectors traditionally determine the dominant chemical
composit ion of the ultrahigh energy cosmic ray flux by comparing the averaged
slant depth of the shower maximum, $X_{max}$, as a function of energy to the
slant depths expect ed for various hypothesized primaries. In this paper, we
present a meth... | 0604558v2 |
2006-08-20 | Iron in Hot DA White Dwarfs | We present a study of the iron abundance pattern in hot hydrogen-rich (DA)
white dwarfs. The study is based on new and archival far ultraviolet
spectroscopy of a sample of white dwarfs in the temperature range 30,000 K <
T_eff < 64,000 K. The spectra obtained with the Far Ultraviolet Spectroscopic
Explorer along with s... | 0608416v1 |
2006-12-15 | Strong gravity effects: X-ray spectra, variability and polarimetry | Accreting black holes often show iron line emission in their X-ray spectra.
When this line emission is very broad or variable then it is likely to
originate from close to the black hole. The theory and observations of such
broad and variable iron lines are briefly reviewed here. In order for a clear
broad line to be fo... | 0612435v1 |
2001-09-17 | Improvement of critical current in MgB2/Fe wires by a ferromagnetic sheath | Transport critical current (Ic) was measured for Fe-sheathed MgB2 round
wires. A critical current density of 5.3 x 10^4 A/cm^2 was obtained at 32K.
Strong magnetic shielding by the iron sheath was observed, resulting in a
decrease in Ic by only 15% in a field of 0.6T at 32K. In addition to shielding,
interaction betwee... | 0109283v1 |
2002-05-09 | Self-assembly of Nanometer-scale Magnetic Dots with Narrow Size Distributions on an Insulating Substrate | The self-assembly of iron dots on the insulating surface of NaCl(001) is
investigated experimentally and theoretically. Under proper growth conditions,
nanometer-scale magnetic iron dots with remarkably narrow size distributions
can be achieved in the absence of a wetting layer Furthermore, both the
vertical and latera... | 0205205v1 |
2002-05-28 | Magnetic properties of alpha-iron(II) phthalocyanine | We report on the magnetic properties of the supra-molecular compound iron(II)
phthalocyanine in its alpha-form. dc- and ac-susceptometry measurements and
Mossbauer experiments show that the iron atoms are strongly magnetically
coupled into ferromagnetic Ising chains with very weak antiferromagnetic
interchain coupling.... | 0205587v1 |
2002-07-31 | Magnetic shielding in MgB2/Fe superconducting wires | Transport critical current (Ic) was measured for MgB2/Fe round wires, with
magnetic field oriented perpendicular to the wire and parallel to it.
Measurements were made on a wire with pure MgB2 core and another wire where
MgB2 core was doped with nano-size SiC. This doping strongly improved the
vortex pinning in MgB2. T... | 0207727v1 |
2003-07-31 | The valence state of iron in the Sr2Fe(Mo,W,Ta)O6.0 double-perovskite system: An Fe K-edge and L2,3-edge XANES study | Here we employ both Fe K and L2,3 edge x-ray absorption near-edge structure
(XANES) spectroscopy techniques to clarify that iron in the B-site ordered
double-perovskite halfmetal, Sr2FeMoO6.0, possesses a mixed-valence state,
FeII/III, and accordingly molybdenum a mixed MoV/VI valence state. A reliable
interpretation o... | 0307755v1 |
2004-10-27 | Matrix Assisted Formation of Ferrihydrite Nanoparticles in a Siloxane/Poly(Oxyethylene) Nanohybrid | Matrix-assisted formation of ferrihydrite, an iron oxide hydroxide analogue
of the protein ferritin-core, in a sol-gel derived organic-inorganic hybrid is
reported. The hybrid network (named di-ureasil) is composed of
poly(oxyethylene) chains of different average polymer molecular weights grafted
to siloxane domains by... | 0410695v1 |
2005-02-17 | Evidence for differentiation in the iron-helicoidal-chain in GdFe$_{3}$(BO$_{3}$)$_{4}$ | We report on a single-crystal X-ray structure study of $GdFe_{3}(BO_{3})_{4}$
at room temperature and at T=90 K. At room temperature $GdFe_{3}(BO_{3})_{4}$
crystallizes in a trigonal space group R32 (No. 155), the same as found for
other members of iron-borate family $RFe_{3}(BO_{3})_{4}$. At 90 K the
structure of $GdF... | 0502423v2 |
2005-04-27 | The nature of iron-oxygen vacancy defect centers in PbTiO3 | The iron(III) center in ferroelectric PbTiO3 together with an oxygen vacancy
forms a charged defect associate, oriented along the crystallographic c-axis.
Its microscopic structure has been analyzed in detail comparing results from a
semi-empirical Newman superposition model analysis based on finestructure data
and fro... | 0504728v1 |
2005-07-22 | Interaction between superconductor and ferromagnetic domains in iron sheath: peak effect in MgB2/Fe wires | Interaction between the superconductor and ferromagnet in MgB2/Fe wires
results in either a plateau or a peak effect in the field dependence of
transport critical current, Ic(H). This is in addition to magnetic shielding of
external field. Current theoretical models cannot account for the observed peak
effect in Ic(H).... | 0507510v1 |
2006-02-13 | Magnetic properties of polymerized C$_{60}$ with Fe | We provide evidence that high-pressure high-temperature (2.5 GPa and 1040 K)
treatment of mixtures of iron with fullerene powders leads to the complete
transformation of iron into iron carbide Fe$_3$C. The comparison of the
magnetic properties (Curie temperature and magnetic moment) of the here studied
samples and thos... | 0602306v3 |
2006-06-01 | Microstructural characterization and kinetics modelling of vermicular cast irons | Several experimental techniques are used for phase identification and
microstructure characterization of austempered vermicular cast irons (XRD, SEM,
TEM and Mossbauer spectroscopy). Acicular structures were found to be composed
by ferrite and austenite with average sizes compatible with those reported for
bainitic fer... | 0606031v2 |
1999-04-29 | Hadronic Shower Development in Iron-Scintillator Tile Calorimetry | The lateral and longitudinal profiles of hadronic showers detected by a
prototype of the ATLAS Iron-Scintillator Tile Hadron Calorimeter have been
investigated. This calorimeter uses a unique longitudinal configuration of
scintillator tiles. Using a fine-grained pion beam scan at 100 GeV, a detailed
picture of transver... | 9904032v1 |
1999-10-07 | Hadronic Shower Development in Tile Iron-Scintillator Calorimetry | The lateral and longitudinal profiles of hadronic showers detected by a
prototype of the ATLAS Iron-Scintillator Tile Hadron Calorimeter have been
investigated. This calorimeter uses a unique longitudinal configuration of
scintillator tiles. Using a fine-grained pion beam scan at 100 GeV, a detailed
picture of transver... | 9910015v1 |
2002-07-30 | Commissioning of SLAC SLD 45-Degree Chambers | The SLD experiment at the Stanford Linear Accelerator Center had a
significant gap in its muon tracking coverage, provided by the Warm Iron
Calorimeter. Supplemental planes of limited streamer tube chambers were added
to improve the coverage in the vicinity of the gap at 0.65 < |cos(theta)|<
0.85. A software effort to ... | 0207099v1 |
2002-08-08 | Accelerating Muons to 2400 GeV/c with Dogbones Followed by Interleaved Fast Ramping Iron and Fixed Superconducting Magnets | The first acceleration stage for this muon collider scenario includes twenty
passes through a single two GeV Linac. Teardrop shaped arcs of 1.8 Tesla fixed
field magnets are used at each end of the Linac. This dogbone geometry
minimizes muon decay losses because muons pass through shorter arcs when their
gamma boost is... | 0208010v1 |
2002-04-18 | Physical Properties of Iron in the Inner Core | The Earth's inner core plays a vital role in the dynamics of our planet and
is itself strongly exposed to dynamic processes as evidenced by a complex
pattern of elastic structure. To gain deeper insight into the nature of these
processes we rely on a characterization of the physical properties of the inner
core which a... | 0204055v1 |
2007-05-09 | RBS1423 - a new QSO with relativistic reflection from an ionised disk | We present the analysis and results of a 20 ks XMM-Newton observation of
RBS1423. X-ray spectral analysis is used to establish a significantly broadened
relativistic iron K-alpha line from a highly ionised disk. A QSO at z=2.262 was
considered to be the optical counterpart of this ROSAT Bright Survey X-ray
source. Base... | 0705.1267v1 |
2007-05-18 | Simulation of Heme using DFT+U: a step toward accurate spin-state energetics | We investigate the DFT+U approach as a viable solution to describe the
low-lying states of ligated and unligated iron heme complexes. Besides their
central role in organometallic chemistry, these compounds represent a
paradigmatic case where LDA, GGA, and common hybrid functionals fail to
reproduce the experimental mag... | 0705.2743v1 |
2007-07-12 | The First Detailed Abundances for M giants in the inner Bulge from Infrared Spectroscopy | We report the first abundance analysis of 17 M giant stars in the inner
Galactic bulge at $(l,b)=(0\deg,-1\deg)$, based on $R=25,000$ infrared
spectroscopy $(1.5-1.8 ~\mu \rm m)$ using NIRSPEC at the Keck telescope. Based
on their luminosities and radial velocities, we identify these stars with a
stellar population old... | 0707.1855v1 |
2007-07-26 | P-V-T equation of state of epsilon iron and its densities at core conditions | The author's new p-V-T Equation of State is tested against the available
experiments of epsilon iron. The root-mean-square-deviations (RMSD) of the
molar volume, pressure, and temperature are 0.021 cm3, 2.0 GPa and 144.9 K
respectively. Separating the experiments into 200 K ranges the new EoS was
compared to the most w... | 0707.3960v1 |
2007-09-21 | Composition of UHECR and the Pierre Auger Observatory Spectrum | We fit the recently published Pierre Auger ultra-high energy cosmic ray
spectrum assuming that either nucleons or nuclei are emitted at the sources. We
consider the simplified cases of pure proton, or pure oxygen, or pure iron
injection. We perform an exhaustive scan in the source evolution factor, the
spectral index, ... | 0709.3390v2 |
2007-10-17 | Iron abundances from optical Fe III absorption lines in B-type stellar spectra | The role of optical Fe III absorption lines in B-type stars as iron abundance
diagnostics is considered. To date, ultraviolet Fe lines have been widely used
in B-type stars, although line blending can severely hinder their diagnostic
power. Using optical spectra, covering a wavelength range ~ 3560 - 9200 A, a
sample of... | 0710.3252v1 |
2007-10-26 | Neutrons from Piezonuclear Reactions | We report the results obtained by cavitating water solutions of iron salts
(iron chloride and iron nitrate) with different concentrations at different
ultrasound powers. In all cases we detected a neutron radiation well higher
than the background level. The neutron production is perfectly reproducible and
can at some e... | 0710.5115v3 |
2007-11-27 | Broad iron K-alpha emission lines as a diagnostic of black hole spin | We address the ability of broad iron emission lines from black hole accretion
disks to diagnose the spin of the black hole. Using a high-resolution
3-dimensional MHD simulation of a geometrically-thin accretion disk in a
Pseudo-Newtonian potential, we show that both the midplane density and the
vertical column density ... | 0711.4158v1 |
2008-01-24 | Tracing the distribution and evolution of Iron in the IntraCluster Medium | Emission lines in X-ray spectra of clusters of galaxies reveal the presence
of heavy elements in the diffuse hot plasma (ICM) in virial equilibrium in the
dark matter potential well. Thanks to the X-ray satellites Chandra and
XMM-Newton we are now able to measure with good accuracy the distribution and
evolution of Iro... | 0801.3756v1 |
2008-04-25 | Magnetic Excitations in the High Tc Iron Pnictides | We calculate the expected finite frequency neutron scattering intensity based
on the two-sublattice collinear antiferromagnet found by recent neutron
scattering experiments as well as by theoretical analysis on the iron
oxypnictide LaOFeAs. We consider two types of superexchange couplings between
Fe atoms: nearest-neig... | 0804.4115v4 |
2008-05-15 | Orbital fluctuation mechanism for superconductivity in iron-based compounds | We propose orbital fluctuations in a multi-band ground state as the
superconducting pairing mechanism in the new iron-based materials. We develop a
general SU(4) theoretical framework for studying a two-orbital model and
discuss a number of scenarios that may be operational within this orbital
fluctuation paradigm. The... | 0805.2150v2 |
2008-06-04 | RXTE determination of the intermediate polar status of XSS J00564+4548, IGR J17195-4100, and XSS J12270-4859 | Aims: We determine the nature of the intermediate polar candidates XSS
J00564+4548, IGR J17195-4100, and XSS J12270-4859.
Methods: Pointed RXTE observations searched for intermediate polar
characteristics in these candidate systems.
Results: XSS J00564+4548 exhibits a period of 465.68+-0.07 s, which we
interpret as... | 0806.0751v1 |
2008-07-04 | Magnetic Order of the Iron Spins in NdOFeAs | Polarized and unpolarized neutron diffraction measurements have been carried
out to investigate the iron magnetic order in undoped NdOFeAs.
Antiferromagnetic order is observed below 141(6) K, which is in close proximity
to the structural distortion observed in this material. The magnetic structure
consists of chains of... | 0807.0662v2 |
2008-07-10 | Neutron diffraction on antiferromagnetic ordering in single-crystal BaFe2As2 | Neutron diffraction experiments have been carried out on a Sn-flux grown
BaFe2As2 single crystal, the parent compound of the A-122 family of FeAs-based
high-Tc superconductors. A tetragonal to orthorhombic structural phase
transition and a three dimensional long-range antiferromagnetic ordering of the
iron moment, with... | 0807.1743v3 |
2008-08-14 | Determination of the single-ion anisotropy energy in a S = 5/2 kagome antiferromagnet using X-ray absorption spectroscopy | We report x-ray absorption and x-ray linear dichroism measurements at the Fe
L2,3 edges of the geometrically frustrated systems of potassium and hydronium
iron jarosite. Comparison with simulated spectra, involving ligand-field
multiplet calculations modelling the 3d-2p hybridization between the iron ion
and the oxygen... | 0808.1969v2 |
2008-09-18 | Metallicity in the Galactic Center: The Quintuplet cluster | We present a measurement of metallicity in the Galactic center Quintuplet
Cluster made using quantitative spectral analysis of two Luminous Blue
Variables (LBVs). The analysis employs line-blanketed NLTE wind/atmosphere
models fit to high-resolution near-infrared spectra containing lines of H, HeI,
SiII, MgII, and FeII... | 0809.3185v1 |
2008-11-11 | Extreme Sensitivity of Superconductivity to Stoichiometry in FeSe (Fe1+dSe) | The recently discovered iron arsenide superconductors, which display
superconducting transition temperatures as high as 55 K, appear to share a
number of general features with high-Tc cuprates, including proximity to a
magnetically ordered state and robustness of the superconductivity in the
presence of disorder. Here ... | 0811.1613v2 |
2008-11-20 | A novel non-Fermi-liquid state in the iron-pnictide FeCrAs | We report transport and thermodynamic properties of stoichiometric single
crystals of the hexagonal iron-pnictide FeCrAs. The in-plane resistivity shows
an unusual "non-metallic" dependence on temperature T, rising continuously with
decreasing T from ~ 800 K to below 100 mK. The c-axis resistivity is similar,
except fo... | 0811.3439v1 |
2008-12-03 | Novel properties in Josephson junctions involving the cos(kx)cos(ky)-pairing state in iron-pnictides | We propose a trilayer $\pi$-junction that takes advantage of the
unconventional $s_{x^2 y^2}=\cos k_x \cos k_y$ pairing symmetry which changes
sign between electron and hole Fermi pockets in the iron pnictides. In
addition, we also present theoretical results for Andreev bound states in thin
superconductor-normal metal... | 0812.0661v2 |
2008-12-05 | Electronic and lattice dynamical properties of the iron-based superconductors LiFeAs and NaFeAs | The electronic structure and lattice vibrational frequencies of the newly
discovered superconductors, LiFeAs and NaFeAs, are calculated within density
functional theory. We show that in the vicinity of the Fermi energy, the
density of states is dominated by contributions from Fe 3d states. We also
calculate the electro... | 0812.1215v1 |
2008-12-09 | An analysis of electron distributions in galaxy clusters by means of the flux ratio of iron lines FeXXV and XXVI | The interpretation of hard X-ray emission from galaxy clusters is still
ambiguous and different models proposed can be probed using various
observational methods. Here we explore a new method based on Fe line
observations.
Spectral line emissivities have usually been calculated for a Maxwellian
electron distribution.... | 0812.1650v1 |
2009-01-20 | Probing the Ground State Properties of Iron-based Superconducting Pnictides and Related Systems by Muon-Spin Spectroscopy | In this short review, we attempt to give a comprehensive discussion of
studies performed to date by muon-spin spectroscopy (more precisely the
relaxation and rotation technique, also know as \muSR technique) on the
recently discovered layered iron-based superconductors. On one side, \muSR has
been used to characterized... | 0901.3139v2 |
2009-01-22 | Magnon-Mediated Pairing and Isotope Effect in Iron-based Superconductors | Within a minimal model for the iron-based superconductors in which itinerant
electrons interact with a band of local moments, we derive a a general
conclusion for multi-band superconductivity. In a multi-band superconductor,
due to the Adler theorem, the inter-band scattering dominates the intra-band
scattering at the ... | 0901.3538v2 |
2009-01-23 | Anisotropic London Penetration Depth and Superfluid Density in Single Crystals of Iron-based Pnictide Superconductors | In- and out-of-plane magnetic penetration depths were measured in three
iron-based pnictide superconducting systems. All studied samples of both 122
systems show a robust power-law behavior, $\lambda (T) T^n$, with the
sample-dependent exponent n=2-2.5, which is indicative of unconventional
pairing. This scenario could... | 0901.3698v2 |
2009-01-28 | Both accurate and precise gf-values for FeII lines | We present a new set of oscillator strengths for 142 FeII lines in the
wavelength range 4000-8000 A. Our gf-values are both accurate and precise,
because each multiplet was globally normalized using laboratory data
(accuracy), while the relative gf-values of individual lines within a given
multiplet were obtained from ... | 0901.4451v2 |
2009-02-02 | Density Functional Study of the Over-Doped Iron Chalcogenide: TlFe$_{2}$Se$_{2}$ with ThCr$_{2}$Si$_{2}$ structure | We report density functional calculations of electronic structure and
magnetic properties of ternary iron chalcogenide TlFe$_{2}$Se$_{2}$, which
occurs in the ThCr$_{2}$Si$_{2}$ structure and discuss the results in relation
to the iron-based superconductors. The ground state is antiferromagnetic with
checkerboard order... | 0902.0265v1 |
2009-02-04 | Evidence for Three-Dimensionality in the Fermi Surface Topology of Layered Electron Doped Ba(Fe1-XCox)2As2 Iron Superconductors | The electronic structure of electron doped iron-arsenide superconductors
Ba(Fe1- xCox)2As2 has been measured with Angle Resolved Photoemission
Spectroscopy. The data reveal a marked photon energy dependence of points in
momentum space where the bands cross the Fermi energy, a distinctive and direct
signature of three-d... | 0902.0756v3 |
2009-02-21 | Inelastic Neutron Scattering Studies of the Spin and Lattice Dynamics in Iron Arsenide Compounds | Neutrons have played an important role in advancing our understanding of the
pairing mechanism and the symmetry of the superconducting energy gap in the
iron arsenide compounds. Neutron measurements of the phonon density-of-state
are in good agreement with ab initio calculations, provided the magnetism of
the iron atom... | 0902.3760v1 |
2009-04-15 | Direct imaging of the structural domains in iron pnictides AFe2As2 (A = Ca, Sr, Ba) | The parent compounds of recently discovered iron-arsenide superconductors,
$A$Fe$_2$As$_2$ with alkaline earth $A$=Ca, Sr, Ba, undergo simultaneous
structural and magnetic phase transitions at a temperature $T_{SM}$. Using a
combination of polarized light microscopy and spatially resolved high-energy
synchrotron X-ray ... | 0904.2337v2 |
2009-04-26 | The orbital characters of bands in iron-based superconductor BaFe1.85Co0.15As2 | The unconventional superconductivity in the newly discovered iron-based
superconductors is intimately related to its multi-band/multi-orbital nature.
Here we report the comprehensive orbital characters of the low-energy
three-dimensional electronic structure in BaFe$_{1.85}$Co$_{0.15}$As$_2$ by
studying the polarizatio... | 0904.4022v3 |
2009-04-29 | Discovery of Red-Skewed K_alpha iron line in Cyg X-2 with Suzaku | We report on the Suzaku observation of neutron star low-mass X-ray binary
Cygnus X-2 which reveals a presence of the iron K_alpha emission line. The line
profile shows a significant red wing. This discovery increases the number of
neutron star sources where red-skewed iron lines were observed and strongly
suggests that... | 0904.4682v1 |
2009-05-09 | Low ordered magnetic moment by off-diagonal frustration in undoped parent compounds to iron-based high-Tc superconductors | A Heisenberg model over the square lattice recently introduced by Si and
Abrahams to describe local-moment magnetism in the new class of Fe-As high-Tc
superconductors is analyzed in the classical limit and on a small cluster by
exact diagonalization. In the case of spin-1 iron atoms, large enough
Heisenberg exchange in... | 0905.1359v2 |
2009-05-11 | The Microstrain-Doping Phase Diagram of the Iron Pnictides Heterostructures at Atomic Limit | The 3D phase diagram of iron pnictides where the critical temperature depends
on charge density and microstrain in the active FeAs layers is proposed. The
iron pnictides superconductors are shown to be a practical realization of a
heterostructure at the atomic limit made of a superlattice of FeAs layers
intercalated by... | 0905.1631v1 |
2009-05-11 | Orbital-Ordering Induces Structural Phase Transition and the Resistivity Anomaly in Iron Pnictides | We attribute the structural phase transition (SPT) in the parent compounds of
the iron pnictides to orbital ordering. Due to the anisotropy of the $d_{xz}$
and $d_{yz}$ orbitals in the $xy$ plane, a ferro-orbital ordering makes the
orthorhombic structure more energetically favorable, thus inducing the SPT. In
this orbi... | 0905.1704v2 |
2009-05-18 | Superconductivity in Multi-orbital t-J1-J2 Model and its Implications for Iron Pnictides | Motivated by the bad metal behavior of the iron pnictides, we study a
multi-orbital $\mathrm{t-J_1-J_2}$ model and investigate possible singlet
superconducting pairings. Magnetic frustration by itself leads to a large
degeneracy in the pairing states. The kinetic energy breaks this into a
quasi-degeneracy among a reduc... | 0905.2634v3 |
2009-05-18 | Ferro-Orbital Order and Strong Magnetic Anisotropy in the Parent Compounds of Iron-Pnictide Superconductors | The puzzling nature of magnetic and lattice phase transitions of iron
pnictides is investigated via a first-principles Wannier function analysis of
representative parent compound LaOFeAs. A rare ferro-orbital ordering is found
to give rise to the recently observed highly anisotropic magnetic coupling, and
drive the pha... | 0905.2957v2 |
2009-05-19 | Strength of correlations in pnictides and its assessment by theoretical calculations and spectroscopy experiments | LDA+DMFT (Local Density Approximation combined with Dynamical Mean-Field
Theory) computation scheme has been used to calculate spectral properties of
LaFeAsO -- the parent compound of the new high-T_c iron oxypnictides. The
average Coulomb repulsion U=3-4 eV and Hund's exchange J=0.8 eV parameters for
iron 3d electrons... | 0905.3038v1 |
2009-06-12 | Violation of Anderson's Theorem for Sign-Reversing s-Wave State of Iron-Pnictide Superconductors | Based on the five-orbital model, we study the effect of local impurity in
iron pnictides, and find that the interband impurity scattering is promoted by
the d-orbital degree of freedom. This fact means that the fully-gapped
sign-reversing s-wave state, which is predicted by spin fluctuation theories,
is very fragile ag... | 0906.2269v4 |
2009-06-12 | Interplay of inequivalent atomic positions in resonant x-ray diffraction of Fe3BO6 | 'Forbidden' Bragg reflections of iron orthoborate Fe3BO6 were studied
theoretically and experimentally in the vicinity of the iron K edge. Their
energy spectra are explained as resulting from the interference of x-rays
scattered from two inequivalent crystallographic sites occupied by iron ions.
This particular structu... | 0906.2338v1 |
2009-07-26 | Josephson effect between electron-doped and hole-doped iron pnictide single crystals | We have observed the Josephson effect in junctions formed between single
crystals of SrFe1.74Co0.26As2 and Ba0.23K0.77Fe2As2. I-V curves showed
resistively-shunted junction characteristics, and the ac Josephson effect was
observed under microwave irradiation. By applying an in-plane magnetic field,
the critical current... | 0907.4456v1 |
2009-08-06 | Resonance as a probe of the electron superconducting gap in BaFe1.9Ni0.1As2 | The discovery of high-transition temperature (high-Tc) superconductivity near
antiferromagnetism in iron arsenides raised the possibility of an
unconventional superconducting mechansim1-8. The observation of clear Fermi
surfaces and nodeless superconducting gaps by angle resolved photoemission9-12
suggests that electro... | 0908.0954v1 |
2009-08-11 | Influence of thermohaline convection on diffusion-induced iron accumulation in A stars | Atomic diffusion may lead to heavy element accumulation inside stars in
certain specific layers. Iron accumulation in the Z-bump opacity region has
been invoked by several authors to quantitatively account for abundance
anomalies observed in some stars, or to account for stellar oscillations
through the induced $\kappa... | 0908.1534v1 |
2009-09-07 | Spin excitations in the excitonic spin-density-wave state of the iron pnictides | Motivated by the iron pnictides, we examine the spin excitations in an
itinerant antiferromagnet where a spin-density wave (SDW) originates from an
excitonic instability of nested electron-like and hole-like Fermi pockets.
Using the random phase approximation (RPA), we derive the Dyson equation for
the transverse susce... | 0909.1222v2 |
2009-09-25 | The inverse iron-bias in action in Abell 2028 | Recent work based on a global measurement of the ICM properties find evidence
for an increase of the iron abundance in galaxy clusters with temperature
around 2-4 keV. We have undertaken a study of the metal distribution in nearby
clusters in this temperature range, aiming at resolving spatially the metal
content of th... | 0909.4679v1 |
2009-10-02 | Broad iron L-line and X-ray reverberation in 1H0707-495 | A detailed analysis of a long XMM-Newton observation of the Narrow Line
Seyfert 1 galaxy 1H0707-495 is presented, including spectral fitting, spectral
variability and timing studies. The two main features in the spectrum are the
drop at ~ 7 keV and a complex excess below 1 keV. These are well described by
two broad, K ... | 0910.0367v1 |
2009-10-08 | Local density of states and superconducting gap in the iron chalcogenide superconductor Fe$_{1+δ}$Se$_{1-x}$Te$_{x}$ observed by scanning tunneling spectroscopy | We report on the first investigation of the quasiparticle local density of
states and superconducting gap in the iron chalcogenide superconductor
Fe$_{1+\delta}$Se$_{1-x}$Te$_{x}$ ($T_{\mathrm{c}} \sim 14$ K). The surface of
a cleaved crystal revealed an atomic square lattice, superimposed on the
inhomogeneous backgrou... | 0910.1485v3 |
2009-10-09 | Spin-waves in the $J_{1a}-J_{1b}-J_{2}$ orthorombic square-lattice Heisenberg models: Application to the iron pnictide materials | Motivated by the observation of spatially anisotropic exchange constants in
the iron pnictide materials, we study the spin-wave spectra of the
$J_{1a}-J_{1b}-J_{2}$ Heisenberg models on a square-lattice with nearest
neighbor exchange $J_{1a}$ along x and $J_{1b}$ along y axis and a second
neighbor exchange $J_2$. We fo... | 0910.1793v1 |
2009-10-17 | Suzaku Discovery of the Strong Radiative Recombination Continuum of Iron from the Supernova Remnant W49B | We present a hard X-ray spectrum of unprecedented quality of the Galactic
supernova remnant W49B obtained with the Suzaku satellite. The spectrum
exhibits an unusual structure consisting of a saw-edged bump above 8 keV. This
bump cannot be explained by any combination of high-temperature plasmas in
ionization equilibri... | 0910.3302v1 |
2009-10-19 | Structure of Neutron-Scattering Peak in both s++ wave and s+- wave states of an Iron pnictide Superconductor | We study the neutron scattering spectrum in iron pnictides based on the
random-phase approximation in the five-orbital model, for fully-gapped s-wave
states with sign reversal (s+-) and without sign reversal (s++). In the s++
wave state, we find that a prominent hump structure appears just above the
spectral gap, by ta... | 0910.3472v2 |
2009-10-29 | A Theoretical Study on a Reaction of Iron(III) Hydroxide with Boron Trichloride by Ab Initio Calculation | We investigate a reaction of boron trichloride (BCl3) with iron(III)
hydroxide (Fe(OH)3) by ab initio quantum chemical calculation as a simple model
for a reaction of iron impurities in BCl3 gas. We also examine a reaction with
water. We find that compounds such as Fe(Cl)(OBCl2)2(OHBCl2) and
Fe(Cl)2(OBCl2)(OHBCl2) are ... | 0910.5633v1 |
2009-11-03 | Coherence effect in a two-band superconductor: Application to iron pnictides | From a theoretical point of view, we propose an experimental method to
determine the pairing symmetry of iron pnictides. We focus on two kinds of
pairing symmetries, $s_{+-}$ and $s_{++}$, which are strong candidates for the
pairing symmetry of iron pnictides. For each of these two symmetries, we
calculate both the den... | 0911.0528v2 |
2009-11-27 | Unconventional pairing in the iron arsenide superconductors | We use magnetic long range order as a tool to probe the Cooper pair wave
function in the iron arsenide superconductors. We show theoretically that
antiferromagnetism and superconductivity can coexist in these materials only if
Cooper pairs form an unconventional, sign-changing state. The observation of
coexistence in B... | 0911.5183v3 |
2009-12-24 | Band Narrowing and Mott Localization in Iron Oxychalcogenides La2O2Fe2O(Se,S)2 | Bad metal properties have motivated a description of the parent iron
pnictides as correlated metals on the verge of Mott localization. What has been
unclear is whether interactions can push these and related compounds to the
Mott insulating side of the phase diagram. Here we consider the iron
oxychalcogenides La2O2Fe2O... | 0912.4741v2 |
2009-12-30 | Three-band superconductivity and the order parameter that breaks time-reversal symmetry | We consider a model of multiband superconductivity, inspired by iron
pnictides, in which three bands are connected via repulsive pair-scattering
terms. Generically, three distinct superconducting states arise within such a
model. Two of them are straightforward generalizations of the two-gap order
parameter while the t... | 0912.5214v2 |
2009-12-30 | Nanoscale electronic order in iron pnictides | The charge distribution in RFeAsO$_{1-x}$F$_x$ (R=La, Sm) iron pnictides is
probed using As nuclear quadrupole resonance. Whereas undoped and
optimally-doped or overdoped compounds feature a single charge environment, two
charge environments are detected in the underdoped region. Spin-lattice
relaxation measurements sh... | 0912.5495v2 |
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