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2006-02-04 | Comprehensive Analysis of RXTE Data from Cyg X-1: Spectral Index-Quasi-Periodic Oscillation Frequency-Luminosity Correlations | We present timing and spectral analysis of ~ 2.2 Ms of RXTE archival data
from Cyg X-1. Using a generic Comptonization model we reveal that the spectrum
of Cyg X-1 consists of three components: a thermal seed photon spectrum, a
Comptonized part of the seed photon spectrum and the iron line. We find a
strong correlation... | 0602091v1 |
2006-02-27 | Primordial Stellar Feedback and the Origin of Hyper Metal-Poor Stars | The apparent absence of stars in the Milky Way halo with -5 ~< [Fe/H] ~< -4
suggests that the gas out of which the halo stars were born experienced a
period of low or delayed star formation after the local universe was lit up by
the first, metal-free generation of stars (Pop III). Negative feedback owed to
the Pop III ... | 0602597v1 |
2006-04-03 | Analysis of 26 Barium Stars I. Abundances | We present a detailed analysis of 26 barium stars, including dwarf barium
stars, providing their atmospheric parameters (Teff, log g, [Fe/H], vt) and
elemental abundances. We aim at deriving gravities and luminosity classes of
the sample stars, in particular to confirm the existence of dwarf barium stars.
Accurate abun... | 0604036v1 |
2006-04-13 | Extinction and metal column density of HI regions up to redshift z~2 | We used the photometric database of the Sloan Digital Sky Survey (SDSS) to
estimate the reddening of 13 SDSS quasars selected on the basis of the presence
of zinc absorption lines in an intervening Damped Ly alpha (DLA) system. In 5
of these quasars the reddening is detected at ~2 sigma confidence level in two
independ... | 0604296v1 |
2006-05-01 | Broad band X-ray spectrum of KS 1947+300 with BeppoSAX | We present results obtained from three BeppoSAX observations of the
accretion-powered transient X-ray pulsar KS 1947+300 carried out during the
declining phase of its 2000 November -- 2001 June outburst. A detailed spectral
study of KS 1947+300 across a wide X-ray band (0.1--100.0 keV) is attempted for
the first time h... | 0605024v1 |
2006-06-06 | Detailed XMM-Newton Observation of the Cluster of Galaxies Abell 1060 | We present results from the XMM-Newton observation of the non-cooling flow
cluster A1060. Large effective area of XMM-Newton enables us to investigate the
nature of this cluster in unprecedented detail. From the observed surface
brightness distribution, we have found that the gravitational mass distribution
is well des... | 0606115v1 |
2006-07-13 | RHESSI Observations of the Solar Flare Iron-line Feature at 6.7 keV | Analysis of RHESSI 3--10 keV spectra for 27 solar flares is reported. This
energy range includes thermal free--free and free--bound continuum and two line
features, at 6.7keV and 8keV, principally due to highly ionized iron (Fe). We
used the continuum and the flux in the so-called Fe-line feature at 6.7keV to
derive th... | 0607309v1 |
2006-07-17 | Chemical Evolution of the Galactic Bulge as Derived from High-Resolution Infrared Spectroscopy of K and M Red Giants | We present chemical abundances in K and M red-giant members of the Galactic
bulge derived from high-resolution infrared spectra obtained with the Phoenix
spectrograph on Gemini-South. The elements studied are carbon, nitrogen,
oxygen, sodium, titanium, and iron. The evolution of C and N abundances in the
studied red-gi... | 0607393v1 |
2006-08-24 | Fall-back crust around a quark-nova compact remnant I: The degenerate shell case with applications to SGRs, AXPs and XDINs | We explore the formation and evolution of debris ejected around quark stars
in the Quark Nova scenario, and the application to Soft Gamma-ray Repeaters
(SGRs) and Anomolous X-ray Pulsars (AXPs). If an isolated neutron star explodes
as a Quark Nova, an Iron-rich shell of degenerate matter forms out of the
fall-back (cru... | 0608536v4 |
2006-09-18 | The Sun is a plasma diffuser that sorts atoms by mass | The Sun is a magnetic plasma diffuser that selectively moves light elements
like H and He and the lighter isotopes of each element to its surface. The Sun
formed on the collapsed core of a supernova. It consists mostly of iron,
oxygen, nickel, silicon and sulfur made near the SN core, like the rocky
planets and ordinar... | 0609509v3 |
2006-09-19 | Suzaku observations of the hard X-ray variability of MCG-6-30-15: the effects of strong gravity around a Kerr black hole | Suzaku has, for the first time, enabled the hard X-ray variability of the
Seyfert 1 galaxy MCG-6-30-15 to be measured. The variability in the 14-45 keV
band, which is dominated by a strong reflection hump, is quenched relative to
that at a few keV. This directly demonstrates that the whole reflection
spectrum is much l... | 0609521v1 |
2006-09-26 | Models for the X-ray spectra and variability of luminous accreting black holes | The X-ray spectra of luminous Seyfert 1 galaxies often appear to be
reflection dominated. In a number of Narrow Line Seyfert 1 (NLS1) galaxies and
galactic black holes in the very high state, the variability of the continuum
and of the iron line are decoupled, the reflected component being often much
less variable than... | 0609703v1 |
2006-09-29 | 3D Collapse of Rotating Stellar Iron Cores in General Relativity including Deleptonization and a Nuclear Equation of State | We present results from the first 2D and 3D simulations of the collapse of
rotating stellar iron cores in general relativity employing a
finite-temperature equation of state and an approximate treatment of
deleptonization during collapse. We compare fully nonlinear and conformally
flat spacetime evolution methods and f... | 0609819v2 |
2006-10-02 | Suzaku Observation of Diffuse X-ray Emission from the Carina Nebula | We studied extended X-ray emission from the Carina Nebula taken with the
Suzaku CCD camera XIS on 2005 Aug. 29. The X-ray morphology, plasma temperature
and absorption to the plasma are consistent with the earlier Einstein results.
The Suzaku spectra newly revealed emission lines from various species including
oxygen, ... | 0610024v1 |
2006-11-30 | Mass loss and yield uncertainty in low-mass asymptotic giant branch stars | We investigate the uncertainty in surface abundances and yields of asymptotic
giant branch (AGB) stars. We apply three different mass loss laws to a 1.5
solar mass star of metallicity Z=0.008 at the beginning of the thermally
pulsing asymptotic giant branch (TP-AGB) phase. Efficient third dredge-up is
found even at ver... | 0612005v1 |
2006-12-12 | Abundances and chemical stratification in the atmosphere of the HgMn star HD 175640 | We present the results of a study of the photospheric abundances of the HgMn
star HD 175640, conducted using archival ESO-UVES spectra. A large number of
unblended (titanium, chromium, manganese and iron) lines were studied to search
for the presence of chemical stratification in the atmosphere of this star. The
select... | 0612323v1 |
2007-01-17 | Detailed chemical composition of Galactic Cepheids. A determination of the Galactic abundance gradient in the 8-12 kpc region | The recent introduction of high resolution/large spectral range spectrographs
provided the opportunity to investigate in detail the chemical composition of
classical Cepheids. This paper is focussed on new abundance determinations for
iron and 6 light metals (O, Na, Mg, Al, Si, Ca) in 30 Galactic Cepheids. We
also give... | 0701499v2 |
2001-07-13 | Iron under Earth's core conditions: Liquid-state thermodynamics and high-pressure melting curve | {\em Ab initio} techniques based on density functional theory in the
projector-augmented-wave implementation are used to calculate the free energy
and a range of other thermodynamic properties of liquid iron at high pressures
and temperatures relevant to the Earth's core. The {\em ab initio} free energy
is obtained by ... | 0107307v1 |
2002-11-14 | Ferromagnetism of a graphite nodule from the Canyon Diablo meteorite | There have recently been various reports of weak ferromagnetism in graphite
(1,2) and synthetic carbon materials (3) such as rhombohedral C60 (4), as well
as a theoretical prediction of a ferromagnetic instability in graphene sheets
(5). With very small ferromagnetic signals, it is difficult to be certain that
the orig... | 0211275v1 |
2003-05-29 | Iron valence in double-perovskite (Ba,Sr,Ca)2FeMoO6: Isovalent substitution effect | In the Fe-Mo based B-site ordered double-perovskite, A2FeMoO6.0, with iron in
the mixed-valence II/III state, the valence value of Fe is not precisely fixed
at 2.5 but may be fine-tuned by means of applying chemical pressure at the
A-cation site. This is shown through a systematic 57Fe Mossbauer spectroscopy
study usin... | 0305679v1 |
2005-10-21 | Carbon diffusion in alpha-iron: Evidence for quantum mechanical tunneling | Recent experimental data on the diffusion coefficient of carbon in alpha-iron
below liquid nitrogen temperature (LNT) question the classical approach to the
observed temperature dependence. As the temperature is lowered below LNT, the
diffusion constant tends to a nearly temperature-independent value rather than
contin... | 0510589v1 |
2006-12-11 | Chemical ordering and composition fluctuations at the (001) surface of the Fe-Ni Invar alloy | We report on a study of (001) oriented fcc Fe-Ni alloy surfaces which
combines first-principles calculations and low-temperature STM experiments.
Density functional theory calculations show that Fe-Ni alloy surfaces are
buckled with the Fe atoms slightly shifted outwards and the Ni atoms inwards.
This is consistent wit... | 0612262v1 |
2007-03-21 | Optical spectra, crystal-field parameters, and magnetic susceptibility of the new multiferroic NdFe3(BO3)4 | We report high-resolution optical absorption spectra for NdFe3(BO3)4 trigonal
single crystal which is known to exhibit a giant magnetoelectric effect below
the temperature of magnetic ordering TN = 33 K. The analysis of the
temperature-dependent polarized spectra reveals the energies and, in some
cases, symmetries and ... | 0703549v1 |
2007-04-03 | Diffuse X-ray Emission from the Carina Nebula Observed with Suzaku | A number of giant HII regions are associated with soft diffuse X-ray
emission. Among these, the Carina nebula possesses the brightest soft diffuse
emission. The required plasma temperature and thermal energy can be produced by
collisions or termination of fast winds from main-sequence or embedded young O
stars, but the... | 0704.0346v1 |
2007-04-12 | Possible X-ray diagnostic for jet/disk dominance in Type 1 AGN | Using Rossi X-ray Timing Explorer Seyfert 1 and 1.2 data spanning 9 years, we
study correlations between X-ray spectral features. The sample consists of 350
time-resolved spectra from 12 Seyfert 1 and 1.2 galaxies. Each spectrum is
fitted to a model with an intrinsic powerlaw X-ray spectrum produced close to
the centra... | 0704.1587v1 |
2007-05-12 | Iron line profiles and self-shadowing from relativistic thick accretion discs | We present Fe Kalpha line profiles from and images of relativistic discs with
finite thickness around a rotating black hole using a novel code. The line is
thought to be produced by iron fluorescence of a relatively cold X-ray
illuminated material in the innermost parts of the accretion disc and provides
an excellent d... | 0705.1796v2 |
2007-06-08 | Evolution of interstellar dust and stardust in the solar neighbourhood | The abundance evolution of interstellar dust species originating from stellar
sources and from condensation in molecular clouds in the local interstellar
medium of the Milky Way is studied and the input of dust material to the Solar
System is determined. A one-zone chemical evolution model of the Milky Way for
the elem... | 0706.1155v1 |
2007-08-06 | On the relativistic iron line and soft excess in the Seyfert 1 galaxy Markarian 335 | We report on a 133 ks XMM-Newton observation of the Seyfert 1 galaxy
Markarian 335. The 0.4-12 keV spectrum contains an underlying power law
continuum, a soft excess below 2 keV, and a double-peaked iron emission feature
in the 6-7 keV range. We investigate the possibility that the double-peaked
emission might represen... | 0708.0751v1 |
2007-08-28 | The Symbiotic System SS73 17 Seen with Suzaku | We observed with Suzaku the symbiotic star SS73 17, motivated by the
discovery by the INTEGRAL satellite and the Swift BAT survey that it emits hard
X-rays. Our observations showed a highly-absorbed X-ray spectrum with NH >
10^23 cm-2, equivalent to A_V > 26, although the source has B magnitude 11.3
and is also bright ... | 0708.3833v1 |
2007-10-03 | Abundance Patterns in Stars in the Bulge and Galactic Center | We discuss oxygen and iron abundance patterns in K and M red-giant members of
the Galactic bulge and in the young and massive M-type stars inhabiting the
very center of the Milky Way. The abundance results from the different bulge
studies in the literature, both in the optical and the infrared, indicate that
the [O/Fe]... | 0710.0866v1 |
2007-10-24 | About Compiled Catalogue of Spectroscopically Determined $α$-Elements Abundances for Stars with Accurate Parallaxes | We present a new version of the compiled catalogue of nearby stars for which
was published the spectoscopically determined effective temperatures, surface
gravities, and abundances of iron, magnesium, calcium, silicon, and titanium.
Distances, velocity components, galactic orbital elements, and ages was
calculated for ... | 0710.4531v1 |
2007-10-25 | Spectral analysis of LMC X-2 with XMM/Newton: unveiling the emission process in the extragalactic Z-source | We present the results of the analysis of an archival observation of LMC X-2
performed with XMM/Newton. The spectra taken by high-precision instruments have
never been analyzed before. We find an X-ray position for the source that is
inconsistent with the one obtained by ROSAT, but in agreement with the Einstein
positi... | 0710.4934v1 |
2007-10-30 | On variability and spectral distortion of the fluorescent iron lines from black-hole accretion discs | We investigate properties of iron fluorescent line arising as a result of
illumination of a black hole accretion disc by an X-ray source located above
the disc surface. We study in details the light-bending model of variability of
the line, extending previous work on the subject.
We indicate bending of photon traject... | 0710.5578v2 |
2007-12-01 | Linear arrays of non homogeneous Cu sites in the CuO2 plane, a new scenario for pairing mechanisms in a currugated-iron-like plane | Experimental results obtained by using x-ray absorption spectroscopy show
that the configurations of Cu sites in the CuO2 plane of Bi 2:2:1:2 high Tc
superconductors are not homogeneous. Different Cu sites are characterized by
short 0.23 nm and long 0.245 nm Cu-O(apical) distances. The linear arrays of
different Cu sit... | 0712.0065v1 |
2007-12-18 | Neutrino oscillation signatures of oxygen-neon-magnesium supernovae | We discuss the flavor conversion of neutrinos from core collapse supernovae
that have oxygen-neon-magnesium (ONeMg) cores. Using the numerically calculated
evolution of the star up to 650 ms post bounce, we find that, for the normal
mass hierarchy, the electron neutrino flux in a detector shows signatures of
two typica... | 0712.3000v3 |
2008-01-31 | Cosmic ray velocity and electric charge measurements with the AMS/RICH detector: prototype results | The Alpha Magnetic Spectrometer (AMS) to be installed on the International
Space Station (ISS) will measure charged cosmic ray spectra of elements up to
iron, in the rigidity range from 1 GV to 1 TV, for at least three years. AMS is
a large angular spectrometer composed of different subdetectors, including a
proximity ... | 0801.4952v1 |
2008-01-31 | Cosmological black hole spin evolution by mergers and accretion | Using recent results from numerical relativity simulations of black hole
mergers, we revisit previous studies of cosmological black hole spin evolution.
We show that mergers are very unlikely to yield large spins, unless alignment
of the spins of the merging holes with the orbital angular momentum is very
efficient. We... | 0802.0025v2 |
2008-02-07 | On the Dynamical Origin of the ICM Metallicity Evolution | We present a study on the origin of the metallicity evolution of the
intra-cluster medium (ICM) by applying a semi-analytic model of galaxy
formation to N-body/SPH (smoothed particle hydrodynamic) non-radiative
numerical simulations of clusters of galaxies. The semi-analytic model includes
gas cooling, star formation, ... | 0802.0975v1 |
2008-02-15 | Evolution of the metal content of the intra-cluster medium with hydrodynamical simulations | We present a comparison between simulation results and X-ray observational
data on the evolution of the metallicity of the intra-cluster medium (ICM). The
simulations of galaxy clusters were performed with the Tree-SPH Gadget2 code
that includes a detailed model of chemical evolution, by assuming three
different shapes... | 0802.2224v1 |
2008-02-25 | NLTE Model of NGC 6543's Central Star and its Relation with the Surrounding Planetary Nebula | We analyze the chemical composition of the central star of the planetary
nebula NGC 6543 based upon a detailed NLTE model of its stellar wind. The
logarithmic abundances by number are H=12.00, He=11.00, C=9.03, N=8.36, O=9.02,
Si=8.19, P=5.53, S=7.57 and Fe=7.24. Compared with the solar abundances, most
of the elements... | 0802.3692v1 |
2008-03-04 | The Chemical Evolution of Dwarf Spheroidal Galaxies: Dissecting the Inner Regions and their Stellar Populations | Using 3-dimensional hydrodynamical simulations of isolated dwarf spheroidal
galaxies (dSphs), we undertake an analysis of the chemical properties of their
inner regions, identifying the respective roles played by Type Ia (SNe Ia) and
Type II (SNe II) supernovae. The effect of inhomogeneous pollution from SNe Ia
is show... | 0803.0385v1 |
2008-03-20 | Tracing the [FeII]/[NeII] ratio and its relationship with other ISM indicators within star forming dwarf galaxies: a Spitzer IRS archival study | Archival Spitzer observations of 41 starburst galaxies that span a wide range
in metallicity reveal for the first time a correlation between the
[FeII]/[NeII] 26.0/12.8 micron ratio and the electron gas density as traced by
the 18.7/33.4 micron [SIII] ratio, with the [FeII]/[NeII] ratio decreasing with
increasing gas d... | 0803.3000v1 |
2008-03-31 | A Generic Two-band Model for Unconventional Superconductivity and Spin-Density-Wave Order in Electron and Hole Doped Iron-Based Superconductors | Based on experimental data on the newly synthesized iron-based
superconductors and the relevant band structure calculations, we propose a
minimal two-band BCS-type Hamiltonian with the interband Hubbard interaction
included. We illustrate that this two-band model is able to capture the
essential features of unconventio... | 0803.4346v3 |
2008-04-04 | Magnetic Order versus superconductivity in the Iron-based layered La(O1-xFx)FeAs systems | In high-transition temperature (high-Tc) copper oxides, it is generally
believed that antiferromagnetism plays a fundamental role in the
superconducting mechanism because superconductivity occurs when mobile
electrons or holes are doped into the antiferromagnetic parent compounds. The
recent discovery of superconductiv... | 0804.0795v1 |
2008-04-14 | The candidate filament close to the 3C295 galaxy cluster: optical and X-ray spectroscopy | We present a detailed analysis of the overdensity of X-ray sources colse to
the 3C 295 galaxy cluster (z=0.46) to assess whether it is associated with a
filament of the large-scale structure of the Universe. We obtained optical
spectra of the optical counterparts of eleven sources associated with the
filament, finding ... | 0804.2143v1 |
2008-04-23 | Specific heat of the iron-based high-$T_c$ superconductor SmO$_{1-x}$F$_x$FeAs | The specific heat $C(T)$ of new iron-based high-$T_c$ superconductor
SmO$_{1-x}$F$_x$FeAs ($0 \leq x \leq 0.2$) was systematically studied. For
undoped $x$ = 0 sample, a specific heat jump was observed at 130 K. This is
attributed to the structural or spin-density-wave (SDW) transition, which also
manifests on resistiv... | 0804.3642v3 |
2008-05-08 | On the peculiar properties of the narrow-line quasar PG 1543+489 | We present the analysis of four XMM-Newton observations of the narrow-line
quasar PG 1543+489 at z=0.400 carried out over a rest-frame time-scale of about
three years. The X-ray spectrum is characterized by a broad, relativistic iron
K_alpha emission line and a steep photon index, which can be both explained by
a ioniz... | 0805.1227v1 |
2008-05-19 | A Brief Comment on the Low-Temperature Structure of LaOFeAs | In a recent paper [arXiv:0804.3569], Takatoshi Nomura {\it et al.} reported a
structural phase transition near 150 K in LaOFeAs and used space group "Cmma"
to describe their X-ray diffraction data. However, they did not discuss how
their proposed structure compares with the early neutron study by Cruz {\it et
al.}[arXi... | 0805.2888v1 |
2008-06-05 | Raman spectra in iron-based quaternary CeO$_{1-x}$F$_x$FeAs and LaO$_{1-x}$F$_x$FeAs | Raman spectra have been measured on iron-based quaternary
CeO$_{1-x}$F$_x$FeAs and LaO$_{1-x}$F$_x$FeAs with varying fluorine doping at
room temperatures. A group analysis has been made to clarify the optical modes.
Based on the first principle calculations, the observed phonon modes can be
assigned accordingly. In LaO... | 0806.0885v1 |
2008-06-19 | 75As NQR/NMR Studies on Oxygen-deficient Iron-based Oxypnictide Superconductors LaFeAsO_{1-y} (y=0,0.25,0.4) and NdFeAsO_{0.6} | We report 75As-NQR/NMR studies on the oxygen-deficient iron(Fe)-based
oxypnictide superconductors LaFeAsO_{0.6} (T_c=28 K) along with the results on
LaFeAsO, LaFeAsO_{0.75}(T_c=20 K) and NdFeAsO_{0.6}(T_c=53 K). Nuclear
spin-lattice relaxation rate 1/T_1 of 75As NQR at zero field on LaFeAsO_{0.6}
has revealed a T^3 dep... | 0806.3238v2 |
2008-07-03 | XMM-Newton X-ray spectra of the SNR 0509-67.5: data and models | We report on X-ray observations of the supernova remnant 0509-67.5 in the
Large Magellanic Cloud with XMM-Newton X-ray observatory. We use the imaging
spectroscopy (EPIC) and Reflective Grating Spectrometer (RGS) data to
investigate properties of the remnant and its environment. The X-ray spectra
were analyzed with SPE... | 0807.0579v1 |
2008-07-07 | Local moment versus Kondo behavior of the 4f-electrons in rare-earth iron oxypnictides | We consider the role played by the 4f states in the rare-earth oxyarsenides
REOFeAs (RE=Ce,Pr,Nd) and the oxyphosphate CeOFeP, using a first-principles
technique that combines the local density approximation and dynamical
mean-field theory (LDA+DMFT). In the Pr and Nd compounds, the 4f states are
located well below and... | 0807.1037v2 |
2008-07-08 | Fe and N self-diffusion in amorphous FeN: A SIMS and neutron reflectivity study | Simultaneous measurement of self-diffusion of iron and nitrogen in amorphous
iron nitride (Fe86N14) using secondary ion mass spectroscopy (SIMS) technique
has been done. In addition neutron reflectivity (NR) technique was employed to
study the Fe diffusion in the same compound. The broadening of a tracer layer
of 57Fe8... | 0807.1302v1 |
2008-07-08 | Superconductivity induced by cobalt doping in iron-based oxyarsenides | Chemical doping has recently become a very important strategy to induce
superconductivity especially in complex compounds. Distinguished examples
include Ba-doped La$_2$CuO$_4$ (the first high temperature superconductor),
K-doped BaBiO$_3$, K-doped C$_{60}$ and Na$_{x}$CoO$_{2}\cdot y$H$_{2}$O. The
most recent example ... | 0807.1304v2 |
2008-07-24 | Resonant Spin Excitation in the High Temperature Superconductor Ba0.6K0.4Fe2As2 | The recent observations of superconductivity at temperatures up to 55K in
compounds containing layers of iron arsenide have revealed a new class of high
temperature superconductors that show striking similarities to the more
familiar cuprates. In both series of compounds, the onset of superconductivity
is associated wi... | 0807.3932v1 |
2008-07-25 | Element-Specific Phonon Density of States of Iron in LaFeAsO_{1-x}F_{x} and La_{1-x}Ca_{x}FePO | We have measured element-specific Fe-phonon densities of states (Fe-PDOS) of
LaFeAsO_{1-x}F_{x} (x = 0, 0.11) and La_{1-x}Ca_{x}FePO (x = 0.13) by using
nuclear resonant inelastic scattering of synchrotron radiation. The Fe-PDOS of
superconductor LaFeAsO_{0.89}F_{0.11} (Tc = 26 K) and that of
non-superconductor LaFeAsO... | 0807.3968v1 |
2008-07-29 | Experimental Consequences of the S-wave $\cos(k_x) \cdot \cos(k_y)$ Superconductivity in the Iron-Pnictides | The experimental consequences of different order parameters in iron-based
superconductors are theoretically analyzed. We consider both nodeless and nodal
order parameters, with an emphasis on the $\cos(k_x)\cdot \cos(k_y)$ nodeless
order parameter recently derived by two of us. We analyze the effect of this
order param... | 0807.4572v2 |
2008-08-06 | Temperature and Spatial Dependence of the Superconducting and Pseudogap of NdFeAsO0.86F0.14 | The discovery of superconductivity with a critical temperature exceeding 55 K
in the iron-oxypnictides and related compounds has quite suddenly given the
community a new set of materials - breaking the tyranny of copper. This new
class of materials raises fundamental questions related to the origin of the
electron pair... | 0808.0895v1 |
2008-08-18 | (pi,pi)-electronic order in iron arsenide superconductors | The distribution of valence electrons in metals usually follows the symmetry
of an ionic lattice. Modulations of this distribution often occur when those
electrons are not stable with respect to a new electronic order, such as spin
or charge density waves. Electron density waves have been observed in many
families of s... | 0808.2454v3 |
2008-09-01 | Atomic diffusion and mixing in old stars II. Observations of stars in the globular cluster NGC 6397 with VLT/FLAMES-GIRAFFE | Evolutionary trends in the surface abundances of heavier elements have
recently been identified in the globular cluster NGC 6397 ([Fe/H]=-2),
indicating the operation of atomic diffusion in these stars. Such trends
constitute important constraints for the extent to which diffusion modifies the
internal structure and su... | 0809.0317v1 |
2008-10-02 | The Delicate Electronic and Magnetic Structure of the LaOFePn System (Pn = pnictogen) | The occurrence of high temperature superconductivity, and the competition
with magnetism, in stoichiometric and doped LaOFeAs and isostructural
iron-oxypnictides is raising many fundamental questions about the electronic
structure and magnetic interactions in this class of materials. There are now
sufficient experiment... | 0810.0376v1 |
2008-10-09 | Mottness underpins the anomalous optical response of Iron Pnictides | The recent discovery of high-temperature superconductivity (HTSC) in doped
Iron pnictides is the latest example of unanticipated behavior exhibited by
$d$- and $f$-band materials. The symmetry of the SC gap, along with the
mechanism of its emergence from the ``normal'' state is a central issue in this
context. Here, mo... | 0810.1607v1 |
2008-10-15 | Coulomb repulsion and correlation strength in LaFeAsO from Density Functional and Dynamical Mean-Field Theories | 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 for new high-T$_c$ iron oxypnictides. Coulomb
repulsion $U$ and Hund's exchange $J$ parameters for iron 3d electrons were
calculated using ... | 0810.2629v1 |
2008-10-19 | Electronic Structure of New AFFeAs Prototype of Iron Arsenide Superconductors | This work is provoked by recent discovery of new class prototype systems
AFFeAs (A=Sr,Ca) of novel layered ironpnictide High-Tc superconductors
(Tc=36K). Here we report ab initio LDA results for electronic structure of the
AFFeAs systems. We provide detailed comparison between electronic properties of
both new systems ... | 0810.3377v1 |
2008-10-28 | Mixing in Zero and Solar Metallicity Supernovae | Two-dimensional simulations of mixing and fall back in non-rotating massive
stars have been carried out using realistic initial models for the presupernova
star and assuming standard spherically symmetric explosions of 1.2*10^51ergs.
Stars of 15 and 25 solar masses with both primordial and solar composition were
modele... | 0810.5142v1 |
2008-11-10 | The intrinsic electronic phase diagram of iron-oxypnictide superconductors | We present the first comprehensive derivation of the intrinsic electronic
phase diagram of the iron-oxypnictide superconductors in the normal state based
on the analysis of the electrical resistivity $\rho$ of both
LaFeAsO$_{1-x}$F$_x$ and SmFeAsO$_{1-x}$F$_x$ for a wide range of doping. Our
data give clear-cut evidenc... | 0811.1601v3 |
2008-11-13 | Electronic phase separation in the slightly underdoped iron pnictide superconductor Ba(1-x)K(x)Fe(2)As(2) | Here we present a combined study of the slightly underdoped novel pnictide
superconductor Ba(1-x)K(x)Fe(2)As(2) by means of X-ray powder diffraction,
neutron scattering, muon spin rotation (muSR), and magnetic force microscopy
(MFM). Commensurate static magnetic order sets in below Tm ~ 70 K as inferred
from the emerge... | 0811.2224v1 |
2008-11-13 | On the importance of satellite lines to the He-like K ALPHA complex and the G ratio for calcium, iron, and nickel | New, more detailed calculations of the emission spectra of the He-like K
ALPHA complex of calcium, iron and nickel have been carried out using data from
both distorted-wave and R-matrix calculations. The value of the GD ratio (an
extended definition of the G ratio that accounts for the effect of resolved and
unresolved... | 0811.2240v1 |
2009-01-15 | Discovery of a broad iron line in the black-hole candidate Swift J1753.5-0127, and the disk emission in the low/hard state revisited | We analyzed simultaneous archival XMM-Newton and RXTE observations of the
X-ray binary and black hole candidate Swift J1753.5-0127. In a previous
analysis of the same data a soft thermal component was found in the X-ray
spectrum, and the presence of an accretion disk extending close to the
innermost stable circular orb... | 0901.2255v1 |
2009-01-17 | Electrostatic co-assembly of iron oxide nanoparticles and polymers : towards the generation of highly persistent superparamagnetic nanorods | A paradigm proposed recently by Boal et al. (A.K. Boal et al., Nature 404,
746-748, 2000) deals with the possibility to use inorganic nanoparticles as
building blocks for the design and fabrication of colloidal and supracolloidal
assemblies. It is anticipated that these constructs could be made of different
shapes, pat... | 0901.2667v1 |
2009-01-18 | Iron pnictides: Single crystal growth and effect of doping on structural, transport and magnetic properties | We demonstrate the preparation of large, free standing iron pnictide single
crystals with a size up to 20 x 10 x 1 mm3 using solvents in zirconia crucibles
under argon atmosphere. Transport and magnetic properties are investigated to
study the effect of potassium doping on the structural and superconducting
property of... | 0901.2728v3 |
2009-02-01 | Neutron Studies of the Iron-based Family of High TC Magnetic Superconductors | We review neutron scattering investigations of the crystal structures,
magnetic structures, and spin dynamics of the iron-based RFe(As,P)O (R=La, Ce,
Pr, Nd), (Ba,Sr,Ca)Fe2As2, and Fe1+x(Te-Se) systems. On cooling from room
temperature all the undoped materials exhibit universal behavior, where a
tetragonal-to-orthorho... | 0902.0091v2 |
2009-02-02 | Doping dependent Irreversible Magnetic Properties of Ba(Fe1-xCox)2As2 Single Crystals | We discuss the irreversible magnetic properties of self-flux grown
Ba(Fe1-xCox)2As2 single crystals for a wide range of concentrations covering
the whole phase diagram from the underdoped to the overdoped regime, x=0.038,
0.047, 0.058, 0.071, 0.074, 0.10, 0.106 and 0.118. Samples were characterized
by a magneto-optical... | 0902.0201v1 |
2009-02-11 | Non-exponential London penetration depth in Ba$_{1-}$K$_{x}$Fe$_{2}$As$_{2}$ single crystals | We have studied the in- and out-of-plane magnetic penetration depths in the
hole- doped iron based superconductor Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$
($T_{c}\approx$ 30K). The study was performed on single crystals grown from
different fluxes and we find that the results are nearly the same. The in-plane
London penetrati... | 0902.1804v1 |
2009-02-16 | Electronic Structure of the BaFe$_2$As$_2$ Family of Iron Pnictides | We use high resolution angle-resolved photoemission spectroscopy to study the
band structure and Fermi surface topology of the BaFe$_2$As$_2$ iron pnictides.
We observe two electron bands and two hole bands near the X-point, $(\pi,\pi)$
of the Brillouin zone, in the paramagnetic state for different doping levels,
inclu... | 0902.2628v1 |
2009-03-11 | Sub-surface convection zones in hot massive stars and their observable consequences | We study the convection zones in the outer envelope of hot massive stars
which are caused by opacity peaks associated with iron and helium ionization.
We determine the occurrence and properties of these convection zones as
function of the stellar parameters. We then confront our results with
observations of OB stars. A... | 0903.2049v1 |
2009-03-17 | Solar System formation | In this review, three major changes in our understanding of the early history
of the Solar System are presented.
1) Early differentiation: A few recent results support the idea that
protoplanet formation and differentiation occurred partly simultaneously than
CAI formation. First, some iron meteorites, eucrites, and ... | 0903.3008v1 |
2009-03-19 | Classification of quantum phases for the star-lattice antiferromagnet via a projective symmetry group analysis | We study possible quantum ground states of the Heisenberg antiferromagnet on
the star lattice, which may be realized in the recently discovered polymeric
Iron Acetate,
Fe$_3$($\mu_3$-O)($\mu$-OAc)$_6$(H$_2$O)$_3$[Fe$_3$($\mu_3$-O)($\mu$-OAc)$_{7.5}$]$_2\cdot$
7H$_2$O. Even though the Fe$^{\rm III}$ moment in this mater... | 0903.3408v1 |
2009-04-28 | Doping dependence of Normal-state Property in the Iron-based Oxypnictide Superconductors LaFeAsO1-y probed by 57Fe-NMR and 75As-NMR/NQR | We report systematic 57Fe-NMR and 75As-NMR/NQR studies on an underdoped
sample (T_c=20 K), an optimally doped sample (T_c=28 K), and an overdoped
sample (T_c=22 K) of oxygen-deficient iron (Fe)-based oxypnictide
superconductor LaFeAsO_{1-y}$. A microscopic phase separation between
superconducting domains and magnetic d... | 0904.4301v2 |
2009-05-01 | Vortex core states in a minimal two-band model for iron-based superconductors | The pairing symmetry is one of the major issues in the study of iron-based
superconductors. We adopt a minimal two-band tight-binding model with various
channels of pairing interaction, and derive a set of two-band Bogoliubov-de
Gennes (BdG) equations. The BdG equations are implemented in real space and
then solved sel... | 0905.0014v2 |
2009-05-06 | Impurity-induced bound states in iron-based superconductors with s-wave cos(kx)cos(ky) pairing symmetry | Using both the self-consistent Bogoliubov-de Gennes formulation and
non-self-consistent T-matrix approach, we perform a comprehensive investigation
of the in-gap bound states induced by a localized single impurity in iron-based
superconductors. We focus on studying signatures associated with the
unconventional sign-cha... | 0905.0734v2 |
2009-05-20 | A new look on the nature of high-spin to low-spin transition in Fe2O3 | Iron sesquioxide (Fe2O3) displays pressure and temperature induced spin and
structural transitions. Our calculations show that, density functional theory
(DFT), in the generalized gradient approximation (GGA) scheme, is capable of
capturing both the transitions. The ambient pressure corundum type phase
(hematite or alp... | 0905.3414v1 |
2009-06-01 | A Compton-thick Wind in the High Luminosity Quasar, PDS 456 | PDS 456 is a nearby (z=0.184), luminous (L_bol ~10^47 erg/s) type I quasar. A
deep 190 ks Suzaku observation in February 2007 revealed the complex, broad
band X-ray spectrum of PDS 456. The Suzaku spectrum exhibits highly
statistically significant absorption features near 9 keV in the quasar
rest--frame. We show that t... | 0906.0312v1 |
2009-06-17 | The Kondo effect in ferromagnetic atomic contacts | Iron, cobalt and nickel are archetypal ferromagnetic metals. In bulk,
electronic conduction in these materials takes place mainly through the $s$ and
$p$ electrons, whereas the magnetic moments are mostly in the narrow
$d$-electron bands, where they tend to align. This general picture may change
at the nanoscale becaus... | 0906.3135v1 |
2009-07-07 | Doping dependence of heat transport in the iron-arsenide superconductor Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$: from isotropic to strongly $k$-dependent gap structure | The temperature and magnetic field dependence of the in-plane thermal
conductivity $\kappa$ of the iron-arsenide superconductor
Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ was measured down to $T \simeq 50$ mK and up to
$H = 15$ T as a function of Co concentration $x$ in the range 0.048 $ \leq x
\leq $ 0.114. In zero magnetic field... | 0907.1276v2 |
2009-09-09 | Modeling the light curve of the transient SCP06F6 | We consider simple models based on core collapse or pair-formation supernovae
to account for the light curve of the transient SCP06F6. A radioactive decay
diffusion model provides estimates of the mass of the required radioactive
nickel and the ejecta as functions of the unknown redshift. An opacity change
such as by d... | 0909.1798v2 |
2009-09-10 | New identified (3H)4d - (3H)4f transitions of Fe II from UVES spectra of HR 6000 and 46 Aql | The analysis of the high-resolution UVES spectra of the CP stars HR 6000 and
46 Aql revealed the presence of an impressive number of unidentified lines, in
particular in the 5000 - 5400 A region. Because numerous 4d-4f transitions of
FeII lie in this spectral range, and because both stars are iron overabundant,
we inve... | 0909.1936v1 |
2009-09-11 | Direct Evidence for Outflow of Metal-enriched Gas Along the Radio Jets of Hydra A | Using deep Chandra observations of the Hydra A galaxy cluster, we examine the
metallicity structure near the central galaxy and along its powerful radio
source. We show that the metallicity of the intracluster medium is enhanced by
up to 0.2 dex along the radio jets and lobes compared to the metallicity of the
undistur... | 0909.2252v2 |
2009-09-22 | Chemistry of atmospheres formed during accretion of the Earth and other terrestrial planets | We used chemical equilibrium and chemical kinetic calculations to model
chemistry of the volatiles released by heating different types of carbonaceous,
ordinary and enstatite chondritic material as a function of temperature and
pressure. Our results predict the composition of atmospheres formed by
outgassing during acc... | 0909.4050v1 |
2009-10-12 | CCD time-series photometry of the globular cluster NGC 5053: RR Lyrae, Blue Stragglers and SX Phoenicis stars revisited | We report the results of CCD $V$, $r$ and $I$ time-series photometry of the
globular cluster NGC 5053. New times of maximum light are given for the eight
known RR Lyrae stars in the field of our images and their periods are revised.
Their $V$ light curves were Fourier decomposed to estimate their physical
parameters. A... | 0910.2068v1 |
2009-10-21 | Fe I/Fe II ionization equilibrium in cool stars: NLTE versus LTE | Non-local thermodynamic equilibrium (NLTE) line formation for neutral and
singly-ionized iron is considered through a range of stellar parameters
characteristic of cool stars. A comprehensive model atom for Fe I and Fe II is
presented. Our NLTE calculations support the earlier conclusions that the
statistical equilibri... | 0910.3997v1 |
2009-10-22 | Point-contact spectroscopic studies on normal and superconducting AFe_2As_2-type iron-pnictide single crystals | Point-contact Andreev reflection spectroscopy (PCARS) is applied to
investigate the gap structure in iron pnictide single crystal superconductors
of the AFe_2As_2 (A=Ba, Sr) family ("Fe-122"). The observed point-contact
junction conductance curves, G(V), can be divided into two categories: one
where Andreev reflection ... | 0910.4230v2 |
2009-11-01 | Non-equilibrium ionization states in galaxy clusters | X-ray imaging observatories have revealed hydrodynamic structures with linear
scales ~ 10 kpc in clusters of galaxies, such as shock waves in the 1E0657-56
and A520 galaxy clusters and the hot plasma bubble in the MKW 3s cluster. The
future X-ray observatory IXO will resolve for the first time the metal
distribution in... | 0911.0119v1 |
2009-11-17 | Limits on spin determination from disc spectral fitting in GX 339-4 | We attempt to constrain the black hole spin in GX 339-4 from spectral fitting
of disc dominated data using RXTE spectra from the three most recent outbursts.
We use the best current models for the disc emission, including full radiative
transfer through the photosphere rather than assuming that the intrinsic
emission f... | 0911.3281v2 |
2009-12-05 | Abundance Ratios in Stars vs. Hot Gas in Elliptical Galaxies: the Chemical Evolution Modeller Point of View | I will present predictions from chemical evolution model aimed at a
self-consistent study of both optical (i.e. stellar) and X-ray (i.e.gas)
properties of present-day elliptical galaxies. Detailed cooling and heating
processes in the interstellar medium (ISM) are taken into and allow a reliable
modelling of the SN-driv... | 0912.0971v1 |
2009-12-11 | Similarities between structural distortions under pressure and chemical doping in superconducting BaFe2As2 | The discovery of a new family of high Tc materials, the iron arsenides
(FeAs), has led to a resurgence of interest in superconductivity. Several
important traits of these materials are now apparent, for example, layers of
iron tetrahedrally coordinated by arsenic are crucial structural ingredients.
It is also now well ... | 0912.2376v1 |
2009-12-17 | XMM-Newton Observations of X-ray Pulsar Cen X-3 | We present the results of our study of X-ray pulsar Cen X-3 using XMM-Newton
observations. The light curve and the spectrum for this observations were built
and Fe triplet within 6.5-7 keV region was detected. The geometric model of
relativistic accretion disk for iron emission lines Fe I K alpha, Fe XXV and Fe
XXVI in... | 0912.3354v2 |
2009-12-22 | XMM-Newton long-look observation of the narrow line Seyfert 1 galaxy PKS0558-504; I: Spectral analysis | We present results from the spectral analysis of a long XMM-Newton
observation of the radio-loud NLS1 galaxy PKS0558-504. The source is highly
variable, on all sampled time scales. We did not observe any absorption
features in either the soft or hard X-ray band. We found weak evidence for the
presence of an iron line a... | 0912.4416v1 |
2009-12-28 | Warm absorber and truncated accretion disc in IRAS 05078+1626 | X-ray observations of unabsorbed active galactic nuclei provide an
opportunity to explore the innermost regions of supermassive black hole
accretion discs. Our goal in this paper is to investigate the central
environment of a Seyfert 1.5 galaxy IRAS 05078+1626. We studied the
time-averaged spectrum obtained with the EP... | 0912.5165v2 |
2010-01-15 | XMM-Newton unveils the complex iron K alpha region of Mrk 279 | We present the results of a ~160 ks-long XMM-Newton observation of the
Seyfert 1 galaxy Mrk 279. The spectrum shows evidence of both broad and narrow
emission features. The Fe K alpha line may be equally well explained by a
single broad Gaussian (FWHM~10,000 km/s) or by two components: an unresolved
core plus a very br... | 1001.2712v1 |
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