publicationDate stringlengths 1 2.79k | title stringlengths 1 36.5k ⌀ | abstract stringlengths 1 37.3k ⌀ | id stringlengths 9 47 |
|---|---|---|---|
1998-07-08 | Nitrogen Abundances in Damped Ly alpha Galaxies | Nitrogen abundances have been derived in Damped Ly alpha (DLA) galaxies at
Zabs = 2.309, 2.827 and 3.025 toward the QSOs 0100+1300, 1425+6039 and
0347-3819 respectively. The behaviour of nitrogen relative to iron-peak and
alpha-elements has been investigated by considering all the extant NI
determinations for a total o... | 9807082v1 |
1998-08-05 | Observation of Cen A by the Rossi X-ray Timing Explorer | The Rossi X-ray Timing Explorer made a short (10 ks) observation of the radio
galaxy Centaurus A on 14 August 1996. Analysis of the combined 2.5-240 keV
spectrum has revealed a heavily absorbed(NH=9.42+/-0.24 e22 cm-2) primary power
law (index=1.86+/-0.015) and an iron line due to fluorescence of cold matter
(EW=162+/-... | 9808042v1 |
1998-08-10 | Iron line profiles including emission from within the innermost stable orbit of a black hole accretion disc | Reynolds & Begelman (1997) have recently proposed a model in which the broad
and extremely redshifted iron line seen during a deep minimum of the light
curve of the Seyfert 1 galaxy MCG-6-30-15 originates from matter spiralling
into a Schwarzschild black hole, contrary to previous claims that the black
hole may be spin... | 9808089v1 |
1999-01-20 | BeppoSAX Observations of the Radio Galaxy Centaurus A | We present preliminary results from two observations of the radio galaxy
Centaurus A performed by the BeppoSAX satellite. We did not detect any spectral
variation of the nuclear continuum in spite of the long-term flux change (by a
factor 1.3) between the two observations. At both epochs, the nuclear
point-like emissio... | 9901266v1 |
1999-02-01 | The X-ray afterglow of the Gamma-ray burst of May 8, 1997: spectral variability and possible evidence of an iron line | We report the possible detection (99.3% of statistical significance) of
redshifted Fe iron line emission in the X-ray afterglow of Gamma-ray burst
GRB970508 observed by BeppoSAX. Its energy is consistent with the redshift of
the putative host galaxy determined from optical spectroscopy. The line
disappeared about 1 day... | 9902013v1 |
1999-02-03 | Iron line in the afterglow: a key to unveil Gamma-Ray Burst progenitors | The discovery of a powerful and transient iron line feature in the X-ray
afterglow spectra of gamma-ray bursts would be a major breakthrough for
understanding the nature of their progenitors. Piro et al. (1999) and Yoshida
et al. (1999) report such a detection in the afterglow of GRB 970508 and GRB
970828, respectively... | 9902058v1 |
1999-06-27 | Stellar Iron Abundances: non-LTE Effects | We report new statistical equilibrium calculations for Fe I and Fe II in the
atmosphere of Late-Type stars. We used atomic models for Fe I and Fe II having
respectively 256 and 190 levels, as well as 2117 and 3443 radiative
transitions. Photoionization cross-sections are from the Iron Project. These
atomic models were ... | 9906433v1 |
1999-11-22 | The First Five Minutes of a Core Collapse Supernova: Multidimensional Hydrodynamic Models | We present results of high-resolution two-dimensional simulations which
follow the first five minutes of a core collapse supernova explosion in a 15
solar mass blue supergiant progenitor. The computations start shortly after
core bounce and include neutrino-matter interactions by using a light-bulb
approximation for th... | 9911407v1 |
2000-03-13 | X-ray emitting-absorbing media in Seyfert 1 galaxies | Seyfert galaxies have been shown to exhibit a large variety of features in
their X-ray spectra from which the environment of the central engine can be
deduced. We focus on the two following aspects: the Warm Absorber, mainly
responsible of the soft X-ray properties, and the reprocessing/reflecting
plasma medium at the ... | 0003168v1 |
2000-03-14 | SN Ia Enrichment in Virgo Early-Type Galaxies from ROSAT and ASCA Observations | We analyzed nine X-ray bright Virgo early-type galaxies observed by both ASCA
and ROSAT. Through spatially resolved spectroscopy, we determined the radial
temperature profile and abundances of Mg, Si and Fe for six galaxies. The
temperature profiles are consistent with isothermal temperatures outside of a
cooler region... | 0003202v1 |
2000-04-05 | A deep X-ray observation of NGC 4258 and its surrounding field | We present a deep X-ray observation of the low-luminosity active galactic
nucleus in NGC4258 (M106) using ASCA. The soft X-ray spectrum <2keV is
dominated by thermal emission from optically-thin plasma with kT~0.5keV. The
hard X-ray emission is clearly due to a power-law component with photon index
Gamma=1.8 absorbed b... | 0004068v1 |
2000-05-31 | Ionization physics evidence for magnetic flare origin of X-rays in AGN | We present full disk X-ray reflection spectra for two currently popular
accretion flow geometries for AGN -- the lamppost model frequently used to
discuss the iron line reverberation in AGN, and the model where the X-rays are
produced in magnetic flares above a cold accretion disk (AD). The lamppost
spectra contain sev... | 0005603v1 |
2000-09-10 | The Temperature of Nonspherical Circumstellar Dust Grains | The temperatures of prolate and oblate spheroidal dust grains in the
envelopes of stars of various spectral types are calculated. Homogeneous
particles with aspect ratios {\small $a/b \le 10$} composed of amorphous
carbon, iron, dirty ice, various silicates, and other materials are considered.
The temperatures of spher... | 0009149v1 |
2000-09-20 | The Chandra High Energy Transmission Grating Observation of an X-ray Ionization Cone in Markarian 3 | We present a preliminary analysis of the first high-resolution X-ray spectrum
of a Seyfert 2 galaxy, Mkn 3, obtained with the High Energy Transmission
Grating Spectrometer onboard the Chandra X-ray Observatory. The high-energy
spectrum (lambda < 4 Ang) is dominated by reflection of the AGN continuum
radiation in a cold... | 0009323v1 |
2001-04-02 | RXTE monitoring of Centaurus A | We report on the analysis from ~110 ks of X-ray observations of Centaurus A
carried out with the Proportional Counter Array (PCA) and the High Energy X-ray
Timing Experiment (HEXTE) instruments on Rossi X-ray Timing Explorer (RXTE)
during three monitoring campaigns over the last 4 years (10 ks in 1996, 74 ks
in 1998, a... | 0104018v2 |
2001-04-02 | Quasar Evolution and the Baldwin Effect in the Large Bright Quasar Survey | From a large homogeneous sample of optical/UV emission line measurements for
993 quasars from the Large Bright Quasar Survey (LBQS), we study correlations
between emission line equivalent width and both restframe ultraviolet
luminosity (i.e., the Baldwin Effect) and redshift. Our semi-automated spectral
fitting account... | 0104029v1 |
2001-10-16 | XMM-Newton discovery of a sharp spectral feature at ~7 keV in the Narrow-Line Seyfert 1 galaxy 1H 0707-495 | We report the first detection of a sharp spectral feature in a Narrow-Line
Seyfert 1 galaxy. Using XMM-Newton we have observed 1H0707-495 and find a drop
in flux by a factor of more than 2 at a rest-frame energy of ~7 keV without any
detectable narrow Fe K alpha line emission. The energy of this feature suggests
a conn... | 0110367v1 |
2001-10-30 | Iron K Lines from Gamma Ray Bursts | We present models for reprocessing of an intense flux of X-rays and gamma
rays expected in the vicinity of gamma ray burst sources. We consider the
transfer and reprocessing of the energetic photons into observable features in
the X-ray band, notably the K lines of iron. Our models are based on the
assumption that the ... | 0110654v3 |
2002-04-02 | Boron in the Small Magellanic Cloud: A Novel Test of Light Element Production | Hubble Space Telescope STIS observations of the B III resonance line at 2066A
have been obtained and analyzed for two Small Magellanic Cloud (SMC) B-type
stars. While boron is not detected in either star, upper limits to the boron
abundance are set, with 12+log(B/H) le 1.6 for both AV 304 and NGC 346-637. The
upper lim... | 0204026v1 |
2002-05-03 | Compton reflection and iron fluorescence in BeppoSAX observations of Seyfert type 1 galaxies | A sample of nine bright Seyfert 1 and NELG type galaxies, observed with
BeppoSAX, is analyzed to assess on a truly broad band basis (0.1-200 keV) the
issue of the spectral contributions of Compton reflection and iron line
fluorescence from circumnuclear gas. The empirical description adopted for the
direct continuum is... | 0205045v1 |
2002-06-06 | A long hard look at MCG-6-30-15 with XMM-Newton | We present first results from a 325 ks observation of the Seyfert 1 galaxy
MCG-6-30-15 with XMM-Newton and BeppoSAX. The strong, broad, skewed iron line
is clearly detected and is well characterised by a steep emissivity profile
within 6r_g (i.e. 6GM/c^2) and a flatter profile beyond. The inner radius of
the emission a... | 0206095v1 |
2002-11-13 | A stellar relic from the early Milky Way | The chemical composition of the most metal-deficient stars reflects the
composition of the gas from which they formed. These old stars provide crucial
clues to the star formation history and the synthesis of chemical elements in
the early Universe. They are the local relics of epochs otherwise observable
only at very h... | 0211274v1 |
2002-11-24 | The influence of microlensing on the shape of the AGN Fe K-alpha line | We study the influence of gravitational microlensing on the AGN Fe K-alpha
line confirming that unexpected enhancements recently detected in the iron line
of some AGNs can be produced by this effect. We use a ray tracing method to
study the influence of microlensing in the emission coming from a compact
accretion disc ... | 0211523v1 |
2002-12-13 | Chandra Analysis of Abell 496 - No Chemical Gradients Across Cold Fronts | We present the results of a spatially-resolved spectroscopic analysis of the
galaxy cluster Abell 496 with the S3 chip on-board the Chandra satellite. We
confirm the presence of a central positive temperature gradient consistent with
a cooling flow, but with a minimum gas temperature of ~0.5-0.9 keV. The cluster
also e... | 0212332v1 |
2003-01-15 | Feedback Heating in Cluster and Galactic Cooling Flows | Cluster cooling flow models that include both thermal conduction and AGN
heating have lower overall mass cooling rates and simultaneously sustain
density and temperature profiles similar to those observed with no ad hoc mass
dropout. To achieve this agreement, the thermal conductivity must be about 0.35
+/- 0.10 of the... | 0301283v1 |
2003-01-16 | First-generation black-hole-forming supernovae and the metal abundance pattern of a very iron-poor star | It has been proposed theoretically that the first generation of stars in the
Universe (population III) would be as massive as 100 solar masses (100Mo),
because of inefficient cooling of the precursor gas clouds. Recently, the most
iron-deficient (but still carbon-rich) low-mass star -- HE0107-5240 -- was
discovered. If... | 0301315v3 |
2003-01-21 | 3-D Simulations of the Chemical and Dynamical Evolution of the Galactic Bulge | A three-dimensional hydrodynamical N-body model for the formation of the
Galaxy is presented with special attention to the formation of the bulge
component. Starting with cosmologically motivated initial conditions, we obtain
a qualitatively similar stellar system to the Galaxy. Then we analyze the
chemical and kinemat... | 0301404v1 |
2003-06-27 | FeII/MgII Emission Line Ratio in High Redshift Quasars | We present results of the analysis of near infrared spectroscopic
observations of 6 high-redshift quasars (z > 4), emphasizing the measurement of
the ultraviolet FeII/MgII emission line strength in order to estimate the
beginning of intense star formation in the early universe. To investigate the
evolution of the FeII/... | 0306584v1 |
2003-07-07 | A Massive X-Ray Outflow from the Quasar PDS 456 | We report on XMM-Newton spectroscopic observations of the luminous,
radio-quiet quasar PDS 456. The hard X-ray spectrum of PDS 456 shows a deep
absorption trough (constituting 50% of the continuum) at energies above 7 keV
in the quasar rest frame, which can be attributed to a series of blue-shifted
K-shell absorption e... | 0307127v1 |
2003-07-31 | Iron Emission in the z=6.4 Quasar SDSS J114816.64+525150.3 | We present near-infrared J and K-band spectra of the z = 6.4 quasar SDSS
J114816.64+525150.3 obtained with the NIRSPEC spectrograph at the Keck-II
telescope, covering the rest-frame spectral regions surrounding the C IV 1549
and Mg II 2800 emission lines. The iron emission blend at rest wavelength
2900-3000 A is clearl... | 0308005v1 |
2003-08-19 | Modeling the NeIX Triplet Spectral Region of Capella with the Chandra and XMM-Newton Gratings | High resolution X-ray spectroscopy with the diffraction gratings of Chandra
and XMM-Newton offers new chances to study a large variety of stellar coronal
phenomena. A popular X-ray calibration target is Capella, which has been
observed with all gratings with significant exposure times. We gathered
together all availabl... | 0308317v1 |
2003-09-12 | Detection of a Fully-resolved Compton Shoulder of the Iron K-alpha Line in the Chandra X-ray Spectrum of GX 301-2 | We report the detection of a fully-resolved, Compton-scattered emission line
in the X-ray spectrum of the massive binary GX 301-2 obtained with the High
Energy Transmission Grating Spectrometer onboard the Chandra X-ray Observatory.
The iron K-alpha fluorescence line complex observed in this system consists of
an inten... | 0309344v1 |
2003-12-19 | XMM-Newton observations of Sagittarius A East | We present an analysis of a recent XMM-Newton observation of Sgr A East, a
supernova remnant located close to the Galactic Centre. Very high quality X-ray
spectra reveal many emission lines from highly ionized atoms consistent with a
multi-temperature thin thermal plasma in ionization equilibrium. We use a
two-temperat... | 0312541v1 |
2004-02-06 | The Possibility of Emersion of the Outer Layers in a Massive Star Simultaneously with Iron-Core Collapse: A Hydrodynamic Model | We analyze the behavior of the outer envelope in a massive star during and
after the collapse of its iron core into a protoneutron star (PNS) in terms of
the equations of one-dimensional spherically symmetric ideal hydrodynamics. The
profiles obtained in the studies of the evolution of massive stars up to the
final sta... | 0402153v1 |
2004-02-13 | Iron Kalpha emission from the low-luminosity Active Galaxies M81 and NGC 4579 | We report on XMM-Newton spectroscopy of the low-luminosity active galaxies
(LLAGN) M81 and NGC4579 both of which have known black hole masses and
well-sampled spectral energy distributions (SED). The iron Kalpha line profiles
from both the LLAGN can be described in terms of two components - a narrow line
at 6.4 keV and... | 0402327v1 |
2004-05-28 | The soft X-ray absorption lines of the Seyfert 1 galaxy MCG--6-30-15 | The absorption lines in the soft X-ray spectrum of MCG--6-30-15 are studied
using the Reflection Grating Spectrometer data from the 2001 XMM-Newton 320 ks
observation. A line search of the full time-averaged spectrum reveals 51
absorption lines and one emission line. The equivalent widths of the lines are
measured and ... | 0405570v1 |
2004-06-29 | Nucleosynthesis in Fast Expansions of High-Entropy, Proton Rich Matter | We demonstrate that nucleosynthesis in rapid, high-entropy expansions of
proton-rich matter from high temperature and density can result in a wider
variety of abundance patterns than heretofore appreciated. In particular, such
expansions can produce iron-group nuclides, p-process nuclei, or even heavy,
neutron-rich iso... | 0406659v1 |
2004-09-24 | Detection of hard X-ray pulsations and a strong iron K_beta emission line during an extended low state of GX 1+4 | We present here results obtained from a detailed timing and spectral analysis
of three BeppoSAX observations of the binary X-ray pulsar GX 1+4 carried out in
August 1996, March 1997, and August 2000. In the middle of the August 2000
observation, the source was in a rare low intensity state that lasted for about
30 hour... | 0409587v1 |
2004-12-20 | Ultrahigh Energy Nuclei Propagation in a Structured, Magnetized Universe | We compare the propagation of iron and proton nuclei above 10^19 eV in a
structured Universe with source and magnetic field distributions obtained from
a large scale structure simulation and source densities about 10^(-5) Mpc^(-3).
All relevant cosmic ray interactions are taken into account, including
photo-disintegrat... | 0412525v1 |
2004-12-23 | Iron Fluorescent Line Emission from Young Stellar Objects in the Orion Nebula | We present the result of a systematic search for the iron Kalpha fluorescent
line at 6.4 keV among 1616 X-ray sources detected by ultra-deep Chandra
observations of the Orion Nebula Cluster and the obscured Orion Molecular Cloud
1 population as part of the Chandra Orion Ultra-deep Project (COUP). Seven
sources are iden... | 0412608v2 |
2005-03-09 | A broad iron line in the Chandra/HETG spectrum of 4U 1705-44 | We present the results of a Chandra 30 ks observation of the low mass X-ray
binary and atoll source 4U 1705-44. Here we concentrate on the study of
discrete features in the energy spectrum at energies below 3 keV, as well as on
the iron Kalpha line, using the HETG spectrometer on board of the Chandra
satellite. Below 3... | 0503224v1 |
2005-04-26 | Axisymmetric collapse simulations of rotating massive stellar cores in full general relativity: Numerical study for prompt black hole formation | We perform axisymmetric simulations for gravitational collapse of a massive
iron core to a black hole in full general relativity. The iron cores are
modeled by $\Gamma = 4/3$ equilibrium polytrope for simplicity and a parametric
equation of state is adopted during the collapse. Performing simulations for a
wide variety... | 0504567v1 |
2005-06-10 | X-ray Spectral Evolution of Her X-1 in a Low State and the Following Short High State | We analyzed spectral variations of $\sim 8.5$ days long RXTE monitoring
observations of Her X-1 in December 2001. This set of observations enables, for
the first time, frequent continuous monitoring (111 pointings in $\sim 8.5$
days) of the source with RXTE including $\sim 1.7$ days long low state part and
the followin... | 0506227v1 |
2005-09-11 | Evidence for Gravitational Infall of Matter onto the Super-Massive Black Hole in the quasar PG 1211+143? | We report the detection of redshifted iron K-alpha absorption lines in the
Chandra LETG spectrum of the narrow-line quasar, PG 1211+143. The absorption
lines are observed at 4.22 keV and 4.93 keV in the quasar spectrum,
corresponding to 4.56 keV and 5.33 keV in the rest frame of PG 1211+143. From
Monte Carlo simulation... | 0509280v1 |
2005-09-22 | A Compton reflection dominated spectrum in a peculiar accreting neutron star | We report on a puzzling event occurred during a long BeppoSAX observation of
the slow-rotating binary pulsar GX 1+4. During this event, lasting about 1 day,
the source X-ray flux was over a factor 10 lower than normal. The low-energy
pulsations disappeared while at higher energies they were shifted in phase. The
spectr... | 0509692v1 |
2006-08-03 | The Galactic WN stars: Spectral analyses with line-blanketed model atmospheres versus stellar evolution models with and without rotation | CONTEXT: Very massive stars pass through the Wolf-Rayet (WR) stage before
they finally explode. Details of their evolution have not yet been safely
established, and their physics are not well understood. Their spectral analysis
requires adequate model atmospheres, which have been developed step by step
during the past ... | 0608078v1 |
2006-08-25 | Fundamental Parameters and Abundances of Metal-Poor Stars: The SDSS Standard BD +17 4708 | The atmospheric parameters and iron abundance of the Sloan Digital Sky Survey
(SDSS) spectrophotometric standard star BD +17 4708 are critically examined
using up-to-date Kurucz model atmospheres, LTE line formation calculations, and
reliable atomic data. We find Teff = 6141+-50 K, log g = 3.87+-0.08, and
[Fe/H]=-1.74+... | 0608559v1 |
2006-10-05 | XMM-Newton observation of the NLS1 Galaxy Ark 564: I. Spectral analysis of the time-average spectrum | We use the data from a recent, 100 ksec XMM-Newton observation of the Narrow
Line Seyfert 1 galaxy Ark 564 to obtain its time average, X-ray spectrum. The
3-11 keV spectrum is well fitted by a power-law of slope 2.43. We detect a weak
(equivalent width ~80 eV) emission line at ~6.7 keV, which implies emission
from ioni... | 0610154v1 |
2007-03-13 | Gamma ray bursts, supernovae and metallicity in the intergalactic medium | The mean iron abundance observed in the intergalactic medium (IGM) within
galaxy clusters and without galaxy clusters is consistent with the mean amount
of iron per unit volume in the Universe which has been produced by standard
supernova (SN) explosions with a rate proportional to the cosmic star-formation
rate. If mo... | 0703293v3 |
1995-08-10 | Structure and Magnetism of Fe/Si Multilayers Grown by Ion-Beam Sputtering | Ion-beam sputtering has been used to prepare Fe/Si multilayers on a variety
of substrates and over a wide range of temperatures. Small-angle x-ray
diffraction and transmission electron microscopy experiments show that the
layers are heavily intermixed although a composition gradient is maintained.
When the spacer layer... | 9508032v1 |
2000-04-06 | Electronic structure and magnetism of equiatomic FeN | In order to investigate the phase stability of equiatomic FeN compounds and
the structure-dependent magnetic properties, the electronic structure and total
energy of FeN with NaCl, ZnS and CsCl structures and various magnetic
configurations are calculated using the first-principles TB-LMTO-ASA method.
Among all the FeN... | 0004091v1 |
2003-06-04 | Interaction of superconductor with magnetic sheath as a way for improvement of critical current in MgB2/Fe superconductor | Magnesium diboride superconducting wires give the largest critical current
density (Jc) when produced with iron sheath. Because iron is ferromagnetic, it
is expected to improve the field dependence of Jc by shielding of the external
field for low magnetic fields. However, transport and magnetic measurements of
Jc revea... | 0306083v1 |
2003-07-11 | Ab initio Simulations of Fe-based Ferric Wheels | Based on first-principles density-functional theory calculations we
investigate the electronic structure of hexanuclear "ferric wheels" M
Fe_6[N(CH_2 CH_2 O)_3]_6 Cl (M = Li, Na) in their antiferromagnetic ground
state. The electronic structure is presented in form of spin- and site-resolved
local densities of states. ... | 0307292v2 |
2005-09-21 | Effect of iron-doping on spin-state transition and ferromagnetism in Pr$_{0.5}$Ca$_{0.5}$CoO$_{3-δ}$ cobalt oxides | Resistivity and dc magnetization measurements were performed for the
polycrystalline Pr$_{0.5}$Ca$_{0.5}$Co$_{1-x}$Fe$_{x}$O$_{3-\delta}$ ($x$ = 0,
0.05, 0.10 and 0.15) samples. The as-fabricated samples exhibit ferromagnetic
(FM) transition and the transition temperature increases with increasing the
iron doping level... | 0509533v1 |
2006-01-25 | The wave model of martensite growth for the FCC-BCC transformation of iron-based alloys | This book is the first monograph in the scientific literature, dedicated to
the FCC-BCC transformation in iron-based alloys, in which the dynamical
approach is used for the explanation of the martensite growth stage.
The rapid growth of a cooling martensite crystal is considered as a
self-organized process controlled... | 0601569v4 |
2006-03-06 | Magnetism of iron: from the bulk to the monoatomic wire | The magnetic properties of iron (spin and orbital magnetic moments,
magnetocrystalline anisotropy energy) in various geometries and
dimensionalities are investigated by using a parametrized tight-binding model
in an $s$, $p$ and $d$ atomic orbital basis set including spin polarization and
the effect of spin-orbit coupl... | 0603121v1 |
1998-09-24 | Oxygen in the Earth's core: a first principles study | First principles electronic structure calculations based on density
functional theory have been used to study the thermodynamic, structural and
transport properties of solid solutions and liquid alloys of iron and oxygen at
Earth's core conditions. Aims of the work are to determine the oxygen
concentration needed to ac... | 9809036v1 |
2007-07-18 | Chemical Abundances of Luminous Cool Stars in the Galactic Center from High-Resolution Infrared Spectroscopy | We present chemical abundances in a sample of luminous cool stars located
within 30 pc of the Galactic Center. Abundances of carbon, nitrogen, oxygen,
calcium, and iron were derived from high-resolution infrared spectra in the H-
and K-bands. The abundance results indicate that both [O/Fe] and [Ca/Fe] are
enhanced resp... | 0707.2610v1 |
2007-07-19 | Mass-Radius Relationships for Solid Exoplanets | We use new interior models of cold planets to investigate the mass-radius
relationships of solid exoplanets, considering planets made primarily of iron,
silicates, water, and carbon compounds. We find that the mass-radius
relationships for cold terrestrial-mass planets of all compositions we
considered follow a generic... | 0707.2895v1 |
2007-08-27 | Evidence of a Broad Relativistic Iron Line from the Neutron Star Low-Mass X-ray Binary Serpens X-1 | We report on an analysis of XMM-Newton data from the neutron star low mass
X-ray binary (LMXB) Serpens X-1 (Ser X-1). Spectral analysis of EPIC PN data
indicates that the previously known broad iron K$\alpha$ emission line from
this source has a significantly skewed structure with a moderately extended red
wing. The as... | 0708.3648v1 |
2007-10-29 | Search for vertical stratification of metals in atmospheres of blue horizontal-branch stars | The observed abundance peculiarities of many chemical species relative to the
expected cluster metallicity in blue horizontal-branch (BHB) stars presumably
appear as a result of atomic diffusion in the photosphere. The slow rotation
(typically $v\sin{i}<$ 10 km s$^{-1}$) of BHB stars with effective temperatures
$T_{\rm... | 0710.5330v2 |
2008-03-19 | A Laboratory Study of the Reduction of Iron Oxides by Hydrogen | To reduce the emission of greenhouse gases by the steel industry,
particularly for ironmaking, the production of DRI (Direct Reduced Iron) using
hydrogen as the reducing gas instead of carbon monoxide is being considered. In
this context, the reduction of pure hematite by hydrogen was studied at the
laboratory scale, v... | 0803.2831v1 |
2008-04-01 | Studying the X-ray hysteresis in GX 339-4: the disc and iron line over one decade | We report on a comprehensive and consistent investigation into the X-ray
emission from GX 339-4. All public observations in the 11 year RXTE archive
were analysed. Three different types of model - single powerlaw, broken
powerlaw and a disc + powerlaw - were fitted to investigate the evolution of
the disc, along with a... | 0804.0148v1 |
2008-04-25 | The chemical composition of red giant stars in four intermediate-age clusters of the Large Magellanic Cloud | This paper presents the chemical abundance analysis of a sample of 27 red
giant stars located in 4 popolous intermediate-age globular clusters in the
Large Magellanic Cloud, namely NGC 1651, 1783, 1978 and 2173. This analysis is
based on high-resolution (R ~ 47000) spectra obtained with the UVES@VLT
spectrograph. For e... | 0804.4061v1 |
2008-05-08 | The Metal Content of Bulge Field Stars from FLAMES-GIRAFFE Spectra. I. Stellar parameters and Iron Abundances | We determine the iron distribution function (IDF) for bulge field stars, in
three different fields along the Galactic minor axis and at latitudes b=-4 deg,
b=-6 deg, and b=-12 deg. A fourth field including NGC6553 is also included in
the discussion. About 800 bulge field K giants were observed with the GIRAFFE
spectrog... | 0805.1218v1 |
2008-05-13 | Nature and distribution of iron sites in a sodium silicate glass investigated by neutron diffraction and EPSR simulation | The short and medium range structure of a NaFeSi2O6 (NFS) glass has been
investigated by high-resolution neutron diffraction with Fe isotopic
substitution, combined with Empirical Potential Structure Refinement (EPSR)
simulations. The majority (~60%) of Fe is 4-coordinated ([4]Fe) and corresponds
only to ferric iron, F... | 0805.1850v1 |
2008-05-13 | Enrichment and Pre-Heating in Intragroup Gas from Galactic Outflows | We examine metal and entropy content in galaxy groups having T_X~0.5-2 keV in
cosmological hydrodynamic simulations. Our simulations include a
well-constrained prescription for galactic outflows following momentum-driven
wind scalings, and a sophisticated chemical evolution model. Our simulation
with no outflows reprod... | 0805.1938v2 |
2008-06-04 | Evidence for two distinct scales of current flow in polycrystalline Sm and Nd iron oxypnictides | Early studies have found quasi-reversible magnetization curves in
polycrystalline bulk rare-earth iron oxypnictides that suggest either
wide-spread obstacles to intergranular current or very weak vortex pinning. In
the present study of polycrystalline samarium and neodymium rare-earth iron
oxypnictide samples made by h... | 0806.0816v1 |
2008-07-13 | Electronic structure of the iron-based superconductor LaOFeP | The recent discovery of superconductivity in the so-called iron-oxypnictide
family of compounds has generated intense interest. The layered crystal
structure with transition metal ions in planar square lattice form and the
discovery of spin-density-wave order near 130 K seem to hint at a strong
similarity with the copp... | 0807.2009v1 |
2008-07-20 | Nearly Isotropic superconductivity in (Ba,K)Fe2As2 | Superconductivity was recently observed in the iron-arsenic-based compounds
with a superconducting transition temperature (Tc) as high as 56K [1-7],
naturally raising comparisons with the high Tc copper oxides. The copper oxides
have layered crystal structures with quasi-two-dimensional electronic
properties, which led... | 0807.3137v4 |
2008-12-05 | XMM-Newton detects a relativistically broadened iron line in the spectrum of the ms X-ray pulsar SAX J1808.4-3658 | We report on a 63-ks long XMM-Newton observation of the accreting millisecond
pulsar SAX J1808.4-3658 during the latest X-ray outburst which started on
September 21st 2008. The pn spectrum shows a highly significant emission line
in the energy band where the iron K-alpha line is expected, and which we
identify as emiss... | 0812.1149v2 |
2008-12-19 | Fermi surface nesting induced strong pairing in iron-based superconductors | The discovery of high-temperature superconductivity in iron pnictides raised
the possibility of an unconventional superconducting mechanism in multiband
materials. The observation of Fermi-surface(FS)-dependent nodeless
superconducting gaps suggested that inter-FS interactions may play a crucial
role in superconducting... | 0812.3704v2 |
2008-12-30 | Anisotropy of the Optimally-Doped Iron Pnictide Superconductor Ba(Fe0.926Co0.074)2As2 | Anisotropies of electrical resistivity, upper critical field, London
penetration depth and critical currents have been measured in single crystals
of the optimally doped iron pnictide superconductor
Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$, $x$=0.074 and $T_c \sim$23 K. The normal state
resistivity anisotropy was obtained by emp... | 0812.4991v1 |
2009-01-06 | Comparison of Relativistic Iron Line Models | The analysis of the broad iron line profile in the X-ray spectra of active
galactic nuclei and black hole X-ray binaries allows us to constrain the spin
parameter of the black hole. We compare the constraints on the spin value for
two X-ray sources, MCG-6-30-15 and GX 339-4, with a broad iron line using
present relativ... | 0901.0670v1 |
2009-01-30 | Variable partial covering and a relativistic iron line in NGC 1365 | We present a complete analysis of the hard X-ray (2-10 keV) properties of the
Seyfert galaxy NGC 1365, based on a 60 ks XMM-Newton observation performed in
January 2004. The two main results are: 1) We detect an obscuring cloud with
N_H~3.5x10^23 cm^(-2) crossing the line of sight in ~25 ks. This implies a
dimension of... | 0901.4809v1 |
2009-06-08 | Enhanced magnetism, memory and aging in Gold-Iron oxide nanoparticle composites | In this report we present systematic magnetic studies of pure iron oxide
nanoparticles and gold iron oxide nanocomposite with increasing Au particle
size/content. For the magnetic studies of these samples we have measured: (1)
zero field cooled (ZFC) and field cooled (FC) magnetization, (2) ac
susceptibility, (3) magne... | 0906.1497v2 |
2009-07-21 | Normal-State Spin Dynamics and Temperature-Dependent Spin Resonance Energy in an Optimally Doped Iron Arsenide Superconductor | The proximity of superconductivity and antiferromagnetism in the phase
diagram of iron arsenides, the apparently weak electron-phonon coupling and the
"resonance peak" in the superconducting spin excitation spectrum have fostered
the hypothesis of magnetically mediated Cooper pairing. However, since most
theories of su... | 0907.3632v1 |
2009-08-18 | Dense Iron Ejecta and Core-collapse Supernova Explosion in the Young Supernova Remnant G11.2-0.3 | We present the results of near-infrared spectroscopic observations of dense
($\simgt$ 10$^3$ cm$^{-3}$) iron ejecta in the young core-collapse supernova
remnant G11.2-0.3. Five ejecta knots projected to be close to its center show a
large dispersion in their Doppler shifts: two knots in the east are blueshifted
by more... | 0908.2613v1 |
2009-10-05 | Intrinsic iron spread and a new metallicity scale for Globular Clusters | We have collected spectra of about 2000 red giant branch (RGB) stars in 19
Galactic globular clusters (GC) using FLAMES@VLT (about 100 star with GIRAFFE
and about 10 with UVES, respectively, in each GC). These observations provide
an unprecedented, precise, and homogeneous data-set of Fe abundances in GCs. We
use it to... | 0910.0675v1 |
2009-10-14 | Debye temperature of disordered bcc-Fe-Cr alloys | Debye temperature, TD, of Fe100-xCrx disordered alloys with 0<x<99.9 was
determined from the temperature dependence of the centre shift of 57Fe
Mossbauer spectra recorded in the temperature range of 80-300K. Its
compositional dependence shows an interesting non-monotonous behaviour. For
0<x<~45 as well as for ~75<x<~95... | 0910.2544v1 |
2009-10-30 | Spectroscopic properties of cool Ursa Major group members | Until now, most members of the Ursa Major (UMa) group of stars have been
identified by means of kinematic criteria. However, in many cases kinematic
criteria alone are insufficient to ascertain, whether an individual star is
really a member of this group. Since photometric criteria are ineffective in
the case of cool d... | 0910.5913v1 |
2009-11-06 | Black hole accretion disks in the canonical low-hard state | Stellar-mass black holes in the low-hard state may hold clues to jet
formation and basic accretion disk physics, but the nature of the accretion
flow remains uncertain. A standard thin disk can extend close to the innermost
stable circular orbit, but the inner disk may evaporate when the mass accretion
rate is reduced.... | 0911.1151v1 |
2009-11-11 | Truncation of the Inner Accretion Disk around a Black Hole at Low Luminosity | Most black hole binaries show large changes in X-ray luminosity caused
primarily by variations in mass accretion rate. An important question for
understanding black hole accretion and jet production is whether the inner edge
of the accretion disk recedes at low accretion rate. Measurements of the
location of the inner ... | 0911.2240v1 |
2009-11-23 | Magnetic anisotropy determination and magnetic hyperthermia properties of small Fe nanoparticles in the superparamagnetic regime | We report on the magnetic and hyperthermia properties of iron nanoparticles
synthesized by organometallic chemistry. They are 5.5 nm in diameter and
display a saturation magnetization close to the bulk one. Magnetic properties
are dominated by the contribution of aggregates of nanoparticles with respect
to individual i... | 0911.4413v1 |
2009-12-01 | The cluster Terzan 5 as a remnant of a primordial building block of the Galactic bulge | Globular star clusters are compact and massive stellar systems old enough to
have witnessed the entire history of our Galaxy, the Milky Way. Although recent
results suggest that their formation may have been more complex than previously
thought, they still are the best approximation to a stellar population formed
over ... | 0912.0192v1 |
2009-12-23 | Linking dwarf galaxies to halo building blocks with the most metal-poor star in Sculptor | Current cosmological models indicate that the Milky Way's stellar halo was
assembled from many smaller systems. Based on the apparent absence of the most
metal-poor stars in present-day dwarf galaxies, recent studies claimed that the
true Galactic building blocks must have been vastly different from the
surviving dwarf... | 0912.4734v1 |
2010-01-06 | Electronic structure of Fe1.04(Te0.66Se0.34) | We report the electronic structure of the iron-chalcogenide superconductor,
Fe1.04(Te0.66Se0.34), obtained with high resolution angle-resolved
photoemission spectroscopy and density functional calculations. In
photoemission measurements, various photon energies and polarizations are
exploited to study the Fermi surface... | 1001.0855v1 |
2010-01-20 | Atmospheric Chemistry in Giant Planets, Brown Dwarfs, and Low-Mass Dwarf Stars III. Iron, Magnesium, and Silicon | We use thermochemical equilibrium calculations to model iron, magnesium, and
silicon chemistry in the atmospheres of giant planets, brown dwarfs, extrasolar
giant planets (EGPs), and low-mass stars. The behavior of individual Fe-, Mg-,
and Si-bearing gases and condensates is determined as a function of
temperature, pre... | 1001.3639v1 |
2010-03-29 | From (pi, 0) magnetic order to superconductivity with (pi, pi) magnetic resonance in Fe1.02(Te1-xSex) | The iron chalcogenide Fe1+y(Te1-xSex) is structurally the simplest of the
Fe-based superconductors. Although the Fermi surface is similar to iron
pnictides, the parent compound Fe1+yTe exhibits antiferromagnetic order with
in-plane magnetic wave-vector (pi, 0). This contrasts the pnictide parent
compounds where the mag... | 1003.5647v1 |
2010-04-06 | Anisotropic superconducting properties of single-crystalline FeSe0.5Te0.5 | Iron-chalcogenide single crystals with the nominal composition
FeSe$_{0.5}$Te$_{0.5}$ and a transition temperature of $T_{c}\simeq14.6$ K were
synthesized by the Bridgman method. The structural and anisotropic
superconducting properties of those crystals were investigated by means of
single crystal X-ray and neutron po... | 1004.0812v1 |
2010-04-09 | Evidence of a universal and isotropic 2Δ/kBTC ratio in 122-type iron pnictide superconductors over a wide doping range | We have systematically investigated the doping and the directional dependence
of the gap structure in the 122-type iron pnictide superconductors by point
contact Andreev reflection spectroscopy. The studies were performed on single
crystals of Ba1-xKxFe2As2 (x = 0.29, 0.49, and 0.77) and SrFe1.74Co0.26As2 with
a sharp ... | 1004.1445v2 |
2010-08-16 | Second Homologous Series of Iron Pnictide Oxide Superconductors (Fe2As2)(Can+2(Al,Ti)nOy)[n = 2,3,4] | We have discovered a new homologous series of iron pnictide oxides
(Fe2As2)(Can+2(Al,Ti)nOy)[n = 2,3,4]. These compounds have perovskite-like
blocking layers between Fe2As2 layers. The structure of new compounds are
tetragonal with space groups of P4/nmm for n = 2 and 4 and P4mm for n = 3,
which are similar to those of... | 1008.2582v4 |
2010-09-06 | Electron-capture supernovae as the origin of elements beyond iron | We examine electron-capture supernovae (ECSNe) as sources of elements heavier
than iron in the solar system and in Galactic halo stars. Nucleosynthesis
calculations are performed on the basis of thermodynamic histories of mass
elements from a fully self-consistent, two-dimensional (2D) hydrodynamic
explosion model of a... | 1009.1000v2 |
2010-10-08 | Chemical pattern across the young associations ONC and OB1b | Context. Abundances of iron-peak and alpha-elements are poorly known in
Orion, and the available measurements yield contradictory results. Aims. We
measure accurate and homogeneous elemental abundances of the Orion subgroups
ONC and OB1b, and search for abundance differences across the Orion complex.
Methods. We presen... | 1010.1658v1 |
2010-11-07 | Interactions between sub-10 nm iron and cerium oxide nanoparticles and 3T3 fibroblasts : the role of the coating and aggregation state | Recent nanotoxicity studies revealed that the physico-chemical
characteristics of engineered nanomaterials play an important role in the
interactions with living cells. Here, we report on the toxicity and uptake of
the cerium and iron oxide sub-10 nm nanoparticles by NIH/3T3 mouse fibroblasts.
Coating strategies includ... | 1011.1670v1 |
2011-01-04 | Structural Analysis on Iron-Based Superconductor Pr1111 System with Oxygen Deficiency and Flourine Substitution | We have performed structural analyses on iron-based superconductors,
PrFeAsO$_{1-y}$ and PrFeAsO$_{1-x}$F$_x$, systematically, by means of Rietveld
method on neutron powder diffraction data. The shifts of iron ion valence from
+2, $\delta$, are accurately determined from the occupancies of O and
O$_{1-x}$F$_x$ sites ob... | 1101.0636v1 |
2011-01-05 | X-ray reflected spectra from accretion disk models.II. Diagnostic tools for X-ray observations | We present a comprehensive study of the emission spectra from accreting
sources. We use our new reflection code to compute the reflected spectra from
an accretion disk illuminated by X-rays. This set of models covers different
values of ionization parameter, solar iron abundance and photon index for the
illuminating sp... | 1101.1115v1 |
2011-01-27 | Electronic band structure, Fermi surface and elastic properties of polymorphs of new 5.2K iron-free superconductor SrPt2As2 from first principles calculations | By means of the first-principles calculations, we have studied in details the
structural, elastic and electronic properties of the new tetragonal
CaBe2Ge2-type 5.2K superconductor SrPt2As2 in comparison with two hypothetical
SrPt2As2 polymorphs with ThCr2Si2-type structures which differ by atomic
configurations of [Pt2... | 1101.5253v1 |
2011-02-04 | A Novel Large Moment Antiferromagnetic Order in K0.8Fe1.6Se2 Superconductor | The discovery of cuprate high Tc superconductors has inspired searching for
unconventional su- perconductors in magnetic materials. A successful recipe has
been to suppress long-range order in a magnetic parent compound by doping or
high pressure to drive the material towards a quantum critical point, which is
replicat... | 1102.0830v1 |
2011-02-08 | Sodium-oxygen anticorrelation and neutron capture elements in Omega Centauri stellar populations | Omega Centauri is no longer the only globular cluster known to contain
multiple stellar populations, yet it remains the most puzzling. Due to the
extreme way in which the multiple stellar population phenomenon manifests in
this cluster, it has been suggested that it may be the remnant of a larger
stellar system. In thi... | 1102.1653v1 |
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