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2000-10-24 | BeppoSAX observations of Narrow-Line Seyfert 1 galaxies: II. Ionized iron features in Arakelian 564 | The BeppoSAX observations of the bright Narrow-Line Seyfert 1 galaxy Ark 564
are presented along with a high quality optical spectrum taken at the 1.5m
telescope at La Silla. The 0.1-10 keV X-ray spectrum is characterized by a
strong soft component which is best described by blackbody-like emission with a
temperature o... | 0010476v1 |
2000-10-31 | Complex resonance absorption structure in the X-ray spectrum of IRAS13349+2438 | The luminous infrared-loud quasar IRAS 13349+2438 was observed with the
XMM-Newton Observatory as part of the Performance Verification program. The
spectrum obtained by the Reflection Grating Spectrometer (RGS) exhibits broad
(v ~ 1400 km/s FWHM) absorption lines from highly ionized elements including
hydrogen- and hel... | 0010660v1 |
2000-11-17 | Observation of X-ray lines from a Gamma-Ray Burst (GRB991216): Evidence of Moving Ejecta from the Progenitor | We report on the discovery of two emission features observed in the X-ray
spectrum of the afterglow of the gamma-ray burst (GRB) of 16 Dec. 1999 by the
Chandra X-Ray Observatory. These features are identified with the Ly$_{\alpha}$
line and the narrow recombination continuum by hydrogenic ions of iron at a
redshift $z=... | 0011337v1 |
2000-11-30 | Illuminated, and enlightened, by GRB 991216 | We consider models for the generation of the emission line recently
discovered in the X-ray afterglow spectrum of several bursts, and especially of
GRB 991216 observed by Chandra. These observations suggest the presence of
0.1-1 solar masses of iron in the vicinity of the bursts. We show that there
are strong geometric... | 0011580v2 |
2000-12-27 | Galactic chemical abundance evolution in the solar neighborhood up to the Iron peak | We have developed a detailed standard chemical evolution model to study the
evolution of all the chemical elements up to the iron peak in the solar
vicinity. We consider that the Galaxy was formed through two episodes of
exponentially decreasing infall, out of extragalactic gas. In a first infall
episode, with a durati... | 0012505v1 |
2001-05-10 | VLT Observations of Turnoff stars in the Globular Cluster NGC 6397 | VLT-UVES high resolution spectra of seven turnoff stars in the metal-poor
globular cluster NGC 6397 have been obtained. Atmospheric parameters and
abundances of several elements (Li, Na, Mg, Ca, Sc, Ti, Cr, Fe, Ni, Zn and Ba)
were derived for program stars. The mean iron abundance is [Fe/H] = -2.02, with
no star-to-sta... | 0105166v1 |
2001-05-16 | Chandra Observations of Diffuse X-Rays from the Sagittarius B2 Cloud | We present the first Chandra results of the giant molecular cloud Sagittarius
B2 (Sgr B2), located about 100 pc away from the Galactic center. Diffuse X-rays
are clearly separated from one-and-a-half dozen resolved point sources. The
X-ray spectrum exhibits pronounced iron K-shell transition lines at 6.40 keV (K
alpha)... | 0105273v1 |
2001-07-13 | High-Resolution X-Ray Spectroscopy of the Accretion Disk Corona Source 4U 1822-37 | We present a preliminary analysis of the X-ray spectrum of the accretion disk
corona source, 4U 1822-37, obtained with the High Energy Transmission Grating
Spectrometer onboard the Chandra X-ray Observatory. We detect discrete emission
lines from photoionized iron, silicon, magnesium, neon, and oxygen, as well as
a bri... | 0107247v1 |
2001-08-20 | Iron K-alpha Emission from X-ray Reflection: Predictions for Gamma-Ray Burst Models | Recent observations of several gamma-ray burst (GRB) afterglows have shown
evidence for a large amount of X-ray line emitting material, possibly arising
from ionized iron. A significant detection of an X-ray spectral feature, such
as that found in the Chandra observation of GRB 991216, may provide important
constraints... | 0108324v1 |
2001-09-30 | Massive Star Evolution: Nucleosynthesis and Nuclear Reaction Rate Uncertainties | We present a nucleosynthesis calculation of a 25 solar mass star of solar
composition that includes all relevant isotopes up to polonium. In particular,
all stable isotopes and necessary nuclear reaction rates are covered. We follow
the stellar evolution from hydrogen burning till iron core collapse and
simulate the ex... | 0110015v1 |
2001-11-27 | The X-ray Spectrum of Cyg X-2 | The spectra of disc accreting neutron stars generally show complex curvature,
and individual components from the disc, boundary layer and neutron star
surface cannot be uniquely identified. Here we show that much of the confusion
over the spectral form derives from inadequate approximations for
comptonization and for t... | 0111497v1 |
2002-01-18 | Detection of FeO towards SgrB2 | We have observed the J=5-4 ground state transition of FeO at a frequency of
153 GHz towards a selection of galactic sources.
Towards the galactic center source SgrB2, we see weak absorption at
approximately the velocity of other features towards this source (62 km
s$^{-1}$ LSR).
Towards other sources, the results w... | 0201311v1 |
2002-02-01 | Diffuse X-rays in the Galactic center region -- The zoo of iron line clumps, non-thermal filaments and hot plasmas -- | This paper reports the diffuse X-ray features around the Galactic center
observed with Chandra. We confirm the ASCA and Ginga discoveries of the
large-scale thin-thermal plasma with strong lines in the Galactic center
region. In addition, many small clumps of emission lines from neutral (6.4 keV
line) to He-like (6.7 k... | 0202010v1 |
2002-03-12 | Evidence for a relativistic iron line in GRS 1915+105 | We report on the discovery of a relativistic iron K\alpha fluorescent
emission line in the BeppoSAX spectrum of the microquasar GRS 1915+105, taken
on April 19, 1998, when the line was unusually intense. The feature is broad
and skewed, clearly indicating emission from the innermost regions of the
accretion disc. The i... | 0203185v1 |
2002-04-23 | Tables of the partition functions for iron, Fe I -- Fe X | We present extensive tables of the Atomic Partition Function for iron ions,
Fe I -- Fe X, and discuss details of the computational method. Partition
functions are given in wide range of temperatures, 10^3 K < T < 10^6 K, and
lowering of ionization energy (0.001 eV < LIE < 5.0 eV). Our APF take into
account all energy l... | 0204384v1 |
2002-04-30 | Detection of Iron Emission in the z = 5.74 QSO SDSSp J104433.04-012502.2 | We obtained near-infrared spectroscopy of the z=5.74 QSO, SDSSp
J104433.04-012 502.2 with the Infrared Camera and Spectrograph of the Subaru
telescope. The redshift of 5.74 corresponds to a cosmological age of 1.0 Gyr
for the current Lambda-dominated cosmology. We found a similar strength of the
Fe II (3000-3500 A) emi... | 0204505v1 |
2002-05-15 | Galaxy Evolution tool: Construction and Applications | We present a dual-infall galactic chemical evolution model which uses a new
set of stellar yields calculated by Limongi et al (2001) to constrain the
amount of iron-peak elements ejected by massive stars. The age-metallicity
relation, G-dwarf distribution and evolution of abundance ratios are predicted
using Galaxy Evo... | 0205249v1 |
2002-05-24 | The relativistic Iron K-alpha line from an accretion disc onto a static non-baryonic compact object | This paper continues the study of the properties of an accretion disc
rotating around a non-baryonic (assumed super-massive) compact object. This
kind of objects, generically known as boson stars, were earlier proposed as a
possible alternative scenario to the existence of super-masive black holes in
the center of ever... | 0205418v1 |
2002-06-04 | Extreme X-ray Iron Lines in Active Galactic Nuclei | We analyze X-ray spectra of heavily obscured (N_H > 10^{24} cm^{-2}) active
galaxies obtained with Chandra, concentrating on the iron K alpha fluorescence
line. We measure very large equivalent widths in most cases, up to 5 keV in the
most extreme example. The geometry of an obscuring torus of material near the
active ... | 0206071v1 |
2002-07-29 | Cosmic Ray Diffusion from the Galactic Spiral Arms, Iron Meteorites, and a possible climatic connection? | We construct a Galactic cosmic ray (CR) diffusion model while considering
that CR sources reside predominantly in the Galactic spiral arms. We find that
the CR flux (CRF) reaching the solar system should periodically increase each
crossing of a Galactic spiral arm. We search for this signal in the CR exposure
age recor... | 0207637v1 |
2002-09-07 | Iron Emission Lines from Extended X-ray Jets in SS 433: Reheating of Atomic Nuclei | Powerful relativistic jets are among the most ubiquitous and energetic
observational consequences of accretion around supermassive black holes in
active galactic nuclei and neutron stars and stellar-mass black holes in x-ray
binary (XRB) systems. But despite more than three decades of study, the
structure and compositi... | 0209131v1 |
2002-12-01 | Magnetic fields in AGNs and microquasars | Observations of AGNs and microquasars by ASCA, RXTE, Chandra and XMM-Newton
indicate the existence of wide X-ray emission lines of heavy ionized elements
in their spectra. The emission can arise in the inner parts of accretion discs
where the effects of General Relativity (GR) must be counted, moreover such
effects can... | 0212008v2 |
2002-12-26 | On the Galactic Disk Metallicity Distribution from Open Clusters I. New Catalogues and Abundance Gradient | In this paper we have compiled two new open cluster catalogues. In the first
one, there are 119 objects with ages, distances and metallicities available,
while in the second one, 144 objects have both absolute proper motion and
radial velocity data, of which 45 clusters also with metallicity data
available. Taking adva... | 0212542v1 |
2003-02-06 | The history of the iron K-alpha line profile in the Piccinotti AGN ESO198-G24 | This paper presents ASCA (July 1997), XMM-Newton (December 2000) and BeppoSAX
(January 2001) observations of the Piccinotti Seyfert 1 galaxy ESO198-G24. The
BeppoSAX 0.1-200 keV spectrum exhibits reprocessing features, probably produced
by an X-ray illuminated, relativistic accretion disk subtending a solid angle
\~2 p... | 0302117v1 |
2003-05-18 | Spectroscopic Constraints on the Surface Magnetic Field of the Accreting Neutron Star EXO 0748-676 | Gravitationally redshifted absorption lines of Fe XXVI, Fe XXV, and O VIII
were inferred recently in the X-ray spectrum of the bursting neutron star EXO
0748-676. We place an upper limit on the stellar magnetic field based on the
iron lines. The oxygen absorption feature shows a multiple component profile
that is consi... | 0305311v1 |
2003-09-02 | HST/STIS observations of sdBV stars: testing diffusion and pulsation theory | We present the initial results of an abundance analysis of echelle UV spectra
of 5 hot subdwarf B (sdB) stars. These stars have been identified as core
helium burning objects on the extreme Horizontal Branch. Around 5% of sdBs show
short-period acoustic mode oscillations. Models predict that these oscillations
are due ... | 0309062v1 |
2003-09-17 | Infrared emission towards 11 years after outburst: Properties of the circumstellar dust | Detailed models are presented for the late epoch mid infrared (MIR) emission
from collisionally heated grains in the shocked circumstellar gas around SN
1987A. Thermal dust emission from a region of moderate density interior to the
thick inner ring seen with the Hubble Space Telescope (HST) is found to be a
natural exp... | 0309473v1 |
2003-09-30 | Axisymmetric MHD simulations of the collapsar model for gamma-ray bursts | We present results from axisymmetric, time-dependent magnetohydrodynamic
(MHD) simulations of the collapsar model for gamma-ray bursts. We begin the
simulations after the 1.7 MSUN iron core of a 25 MSUN presupernova star has
collapsed and study the ensuing accretion of the 7 MSUN helium envelope onto
the central black ... | 0310002v1 |
2003-10-08 | Determining the Metallicity of Cepheid Stars in the SMC, LMC and the Galaxy | The Cepheid Period-Luminosity relation is unquestionably one of the most
powerful tools at our disposal for determining the extragalactic distance
scale. While significant progress has been made in the past few years towards
its understanding and characterisation, both on the observational (e.g. the HST
Key Project) an... | 0310217v1 |
2003-10-15 | Galactic metallicity distribution from open clusters | We have compiled two new Galactic open cluster catalogues. The first one has
119 objects with age, distance and metallicity data, while the second one has
144 objects with both absolute proper motion and radial velocity data, of which
45 clusters also with metallicity data available. An iron radial gradient of
about $-... | 0310395v1 |
2003-12-10 | Is the soft excess in AGN real? | We systematically analyse all publicly available XMM-Newton spectra of
radio-quiet PG quasars. The soft X-ray excess in these objects is well modelled
by an additional, cool, Compton scattering region. However, the remarkably
constant temperature derived for this component over the whole sample requires
a puzzling fine... | 0312271v2 |
2003-12-18 | New constraints on the mass composition of cosmic rays above 10^17 eV from Volcano Ranch measurements | Linsley used the Volcano Ranch array to collect data on the lateral
distribution of showers produced by cosmic rays at energies above 10^17 eV.
Very precise measurements of the steepness of the lateral distribution function
were made on 366 events. The current availability of sophisticated hadronic
interaction models h... | 0312463v1 |
2004-04-19 | A broad iron K alpha line at z=1.146 | We report the discovery of a strong iron K alpha line in the hard X-ray
selected source CXOJ 123716.7+621733 in the Chandra Deep Field North survey at
z=1.146. The analysis is made possible by the very deep exposure ~2 Ms and low
background of the ACIS detector. The line profile seems to be inconsistent with
a narrow f... | 0404364v1 |
2004-05-13 | On the iron Kalpha complex in magnetic cataclysmic variables | We present a compilation of spectra of the iron Kalpha region in magnetic
cataclysmic variables, using data from the Chandra-HETG. The H-like, He-like
and fluorescent components are clearly resolved, and there are hints of the
structure within each component. The different shape of the He-like component
in AM Her might... | 0405254v1 |
2004-05-21 | Atmospheric parameters and abundances of sdB stars | We summarize recent results of quantitative spectral analyses using NLTE and
metal line-blanketed LTE model atmospheres. Temperatures and gravities derived
for hundreds of sdB stars are now available and allow us to investigate
systematic uncertainties of teff, log g scales and to test the theory of
stellar evolution a... | 0405426v1 |
2004-07-22 | Shot cutoff timescales in different spectral states of Cygnus X-1 | We investigate the shot cutoff timescale evolutions during different spectral
states in the black hole binary Cygnus X-1 with the recently proposed w
spectral analysis technique. For low energy shots, their cutoff timescale
decreases from the low state to intermediate state, and to high state
monotonically. However in ... | 0407470v1 |
2004-07-30 | X-ray Lines in Gamma-ray Bursts and Cerenkov Line Mechanism | X-ray emission and absorption features are of great importance in our
understanding the nature and environment of gamma-ray bursts (GRBs). So far,
iron emission lines have been detected in at least four GRB afterglows. In this
paper, the observational properties and physical constraints on materials
surrounding GRB sou... | 0407626v1 |
2004-09-19 | On the variability of the iron line in Mrk 841 | Petrucci et al. (2002; hereafter P02) have reported extraordinary behaviour
of the iron K alpha line in the type 1 AGN Mrk 841. At the XMM-Newton/EPIC
resolution, a narrow line was observed in a short observation, which then
apparently disappeared around 0.5 days later when another observation was
performed. The limits... | 0409459v1 |
2004-10-28 | Insight into AGB and post-AGB stellar evolution with FUSE | FUSE spectroscopy has proved that extremely hot hydrogen-deficient post-AGB
stars (PG1159 stars) display matter on their surface that usually remains
hidden in the region between the H- and He-burning shells of the former AGB
star. Hence, the spectral analysis of PG1159 stars allows to study directly the
chemistry of t... | 0410689v1 |
2004-11-10 | The Origin, Composition, and Energy Source for the Sun | Heterogeneous supernova debris formed the solar system. Cores of inner
planets formed in the central iron rich region. The Sun formed on the collapsed
supernova core. Lighter elements and the lighter isotopes of each element are
enriched at the solar surface. The most abundant nuclide in the Sun is Iron 56,
the decay p... | 0411255v1 |
2004-11-15 | Iron Abundance in Hydrogen-Rich Central Stars of Planetary Nebulae | We report on an on-going analysis of high-resolution UV spectra of hot
hydrogen-rich central stars of planetary nebulae (CSPN), obtained with the
Hubble Space Telescope and FUSE. Since UV spectra of many CSPN are dominated by
Fe and Ni lines, we intend to use them as temperature indicators to check the
CSPN temperature... | 0411404v1 |
2004-11-18 | A Multiband Approach to AGN: Radioscopy & Radio Astronomy | Only in the radio-loud population of active galactic nuclei (AGN) does the
production, collimation, and acceleration of powerful relativistic jets take
place. We introduce here a concept of combined VLBI- and X-ray spectroscopic
observations of sources with relativistic, broad iron lines. This approach has
enormous pot... | 0411534v1 |
2004-11-25 | Influence of Primary Cosmic Radiation Mass Composition on the Estimation of Eas Energy | At the Yakutsk EAS array E_em is determined by using measurements of EAS
Cherenkov light flux and charged particle flux. It is known from calculations
that these characteristics depend on a sort of primary particle and, therefore,
the estimation of E_em depends on a primary particle mass. In the work the
dependence of ... | 0411682v2 |
2004-12-03 | Narrow Iron K$α$ Lines in Active Galactic Nuclei: Evolving Populations? | We assemble a sample consisting of 66 active galactic nuclei (AGNs) from
literature and the {\em XMM-Newton} archive in order to investigate the origin
of the 6.4 keV narrow iron K$\alpha$ line (NIKAL). The X-ray Baldwin effect of
the NIKAL is confirmed in this sample. We find the equivalent width ($EW$) of
the NIKAL i... | 0412075v1 |
2005-01-10 | West-Side Story (On the History of Density-Wave Spiral Theories in the 1960s) | This paper deals with the history of Density-Wave Spiral Theories in the
1960s. The motivation to write the paper was the publication of two papers on
the history of these theories (Pasha 2004a,b). Pasha's papers tell only a part
of the story that took place on the Western side of the Iron Curtain in the
1960s. But giv... | 0501170v1 |
2005-02-10 | Plasma Diffuser Sorts Light Atoms to Solar Surface | The Sun operates like a giant plasma diffuser that sorts lighter isotopes and
elements to the solar surface. Measurements indicate that the interior of the
Sun consists mostly of the same seven, even-numbered elements as ordinary
meteorites: Iron, oxygen, nickel, silicon, sulfur, magnesium, and calcium.
These ordinary ... | 0502206v1 |
2005-03-28 | A Compiled Catalogue of Spectroscopically Determined Elemental Abundances for Stars with Accurate Parallaxes. I.Magnesium | We present a compiled catalogue of effective temperatures, surface gravities,
iron and magnesium abundances, distances, velocity components, and orbital
elements for stars in the solar neighborhood. The atmospheric parameters and
iron abundances are averages of published values derived from model synthetic
spectra for ... | 0503591v2 |
2005-04-06 | On the periodic clustering of cosmic ray exposure ages of iron meteorites | Two recent papers claimed to have found a periodic variation of the galactic
cosmic ray (CR) flux over the last 1-2 Gyr, using the CR exposure ages of iron
meteorites. This was attributed to higher CR flux during the passage of the
Earth through the spiral arms of the Milky Way, as suggested by models. The
derived peri... | 0504155v1 |
2005-05-27 | Iron Needles in Supernova Remnants? | It has been suggested by Dwek (2004) that iron needles could explain the
submillimetre emission from the Cas A supernova remnant (SNR) with only a very
small total mass. We investigate whether a similar model holds for the Kepler
supernova remnant, and find that its emission could indeed be explained by a
dust mass of ... | 0505557v2 |
2005-05-30 | High-resolution spectroscopy of the old open cluster Collinder 261:abundances of Iron and other elements | We present the analysis of high resolution spectra of six red giant stars in
the old open cluster Collinder 261. Reddening values for individual stars,
derived from the relation between colours and temperatures (deduced from our
fully spectroscopic analysis) are consistent with previous determinations based
on photomet... | 0505606v1 |
2005-06-29 | Oxygen in Galactic Disk Stars: non-LTE abundances from the 777 nm O I triplet | Oxygen abundances for a large sample of dwarf and giant stars kinematically
selected to be part of the Galactic thin and thick disks have been determined
from a non-LTE analysis of the O I triplet lines at 777 nm. The abundance
analysis was performed using the infrared flux method temperature scale,
trigonometric surfa... | 0506744v1 |
2005-07-18 | The X-ray spectra of accreting Kerr black holes | The relativistic broad iron lines seen in the X-ray spectra of several active
galaxies and Galactic black hole systems are reviewed. Most such objects
require emission from within the innermost stable orbit of a non-rotating black
hole, suggesting that the black holes are rapidly spinning Kerr holes. We
discuss the sof... | 0507409v1 |
2005-09-01 | XMM-Newton observation of the bright Seyfert 1 galaxy, MCG+8-11-11 | We report on the XMM-Newton observation of the bright Seyfert 1 galaxy,
MCG+8-11-11. Data from the EPIC/p-n camera, the Reflection Gratings
Spectrometers (RGS) and the Optical Monitor (OM) have been analyzed. The p-n
spectrum is well fitted by a power law, a spectrally unresolved Fe Kalpha line,
a Compton reflection co... | 0509017v1 |
2005-10-05 | Pixie Dust: The Silicate Features in the Diffuse Interstellar Medium | We have analyzed the 9.7 and ``18'' micron interstellar silicate absorption
features along the line of sight toward four heavily extincted galactic WC-type
Wolf-Rayet (WR) stars. We construct two interstellar extinction curves from
1.25 to 25 micron using near-IR extinction measurements from the literature
along with t... | 0510156v1 |
2006-01-04 | ASCA Observations of OAO 1657-415 and its Dust-Scattered X-Ray Halo | We report on two ASCA observations of the high-mass X-ray binary pulsar OAO
1657-415. A short observation near mid-eclipse caught the source in a
low-intensity state, with a weak continuum and iron emission dominated by the
6.4-keV fluorescent line. A later, longer observation found the source in a
high-intensity state... | 0601075v1 |
2006-03-21 | On the Unusual Depletions toward Sk 155, or What Are the Small Magellanic Cloud Dust Grains Made of? | The dust in the Small Magellanic Cloud (SMC), an ideal analog of primordial
galaxies at high redshifts, differs markedly from that in the Milky Way by
exhibiting a steeply rising far-ultraviolet extinction curve, an absence of the
2175 Angstrom extinction feature, and a local minimum at ~12 micron in its
infrared emiss... | 0603573v1 |
2006-04-03 | Detection of Highly Ionized Metal Absorption Lines in the Ultracompact X-ray Dipper 4U 1916-05 | We present the high-resolution Chandra X-ray Observatory persistent (non-dip)
spectrum of 4U 1916-05 which revealed narrow absorption lines from hydrogenic
neon, magnesium, silicon, and sulfur, in addition to the previous identified
hydrogenic and helium-like iron absorption lines. This makes 4U 1916-05 only
the second... | 0604046v1 |
2006-05-09 | The chemical compositions of the extreme halo stars HE0107-5240 and HE1327-2326 inferred from 3D hydrodynamical model atmospheres | We investigate the impact of realistic 3D hydrodynamical model stellar
atmospheres on the determination of elemental abundances in the carbon-rich,
hyper iron-poor stars HE0107-5240 and HE1327-2326. We derive the chemical
compositions of the two stars by means of a detailed 3D analysis of spectral
lines under the assum... | 0605219v1 |
2006-05-25 | On the Iron content of NGC 1978 in the LMC: a metal rich, chemically homogeneous cluster | We present a detailed abundance analysis of giant stars in NGC 1978, a
massive, intermediate-age stellar cluster in the Large Magellanic Cloud,
characterized by a high ellipticity and suspected to have a metallicity spread.
We analyzed 11 giants, all cluster members, by using high resolution spectra
acquired with the U... | 0605646v1 |
2006-07-18 | Dielectronic recombination of Fe^{13+}: benchmarking the M-shell | We have carried-out a series of multi-configuration Breit-Pauli AUTOSTRUCTURE
calculations for the dielectronic recombination of Fe^{13+}. We present a
detailed comparison of the results with the high-energy resolution measurements
reported recently from the Heidelberg Test Storage Ring by Schmidt et al. Many
Rydberg s... | 0607412v1 |
2006-07-20 | RXTE Observations of 1A 1744-361: Correlated Spectral and Timing Behavior | We analyze Rossi X-ray Timing Explorer (RXTE) Proportional Counter Array
(PCA) data of the transient low mass X-ray binary (LMXB) system 1A 1744-361. We
explore the X-ray intensity and spectral evolution of the source, perform
timing analysis, and find that 1A 1744-361 shows `atoll' behavior during the
outbursts. The c... | 0607475v1 |
2006-07-21 | Gravity-mode pulsations in subdwarf B stars: a critical test of stellar opacity | The identification of non-radial g-mode oscillations as the cause of
variability in cool subdwarf B stars (PG1716 variables) has been frustrated by
a 5 000 K discrepancy between the observed and theoretical blue edge of the
instability domain (Fontaine et al. 2003). A major component in the solution to
this problem has... | 0607505v1 |
2006-08-23 | Effect of turbulent diffusion on iron abundance profiles | We compare the observed peaked iron abundance profiles for a small sample of
groups and clusters with the predictions of a simple model involving the metal
ejection from the brightest galaxy and the subsequent diffusion of metals by
stochastic gas motions. Extending the analysis of Rebusco et al. (2005) we
found that f... | 0608491v1 |
2006-10-19 | An XMM-Newton survey of broad iron lines in AGN | We report on the iron K-alpha line properties of a sample of Seyfert galaxies
observed with the XMM-Newton EPIC pn instrument. Using a systematic and uniform
analysis, we find that complexity at iron-K is extremely common in the XMM
spectra. Once appropriate soft X-ray absorption, narrow 6.4 keV emission and
associated... | 0610585v1 |
2006-12-08 | Solar Chemical Peculiarities? | Several investigations of FGK stars in the solar neighborhood have suggested
that thin-disk stars with an iron abundance similar to the Sun appear to show
higher abundances of other elements, such as silicon, titanium, or nickel.
Offsets could arise if the samples contain stars with ages, mean galactocentric
distances,... | 0612200v1 |
2006-12-12 | Relativistic inflow in the Seyfert 1 Mrk 335 revealed through X-ray absorption | The analysis of hard X-ray features in XMM-Newton data of the bright Sy 1
galaxy Mrk 335 is reported here. The presence of a broad, ionised iron K alpha
emission line in the spectrum, first found by Gondoin et al.(2002), is
confirmed. The broad line can be modeled successfully by relativistic accretion
disc reflection ... | 0612315v1 |
2006-12-19 | Heavy metals and lead isotopes in sdB stars | We present a detailed abundance analysis of high-resolution ultraviolet
echelle spectra of five subdwarf B stars obtained with HST-STIS The goal of our
observations was to test the hypothesis that pulsations in sdBs are correlated
to the surface abundances of iron-group elements. We study two pulsators and
three non-pu... | 0612535v1 |
2006-12-19 | Hard X-rays and Fluorescent Iron Emission from the Embedded Infrared Cluster in NGC 2071 | We present first results of XMM-Newton X-ray observations of the infrared
cluster lying near the NGC 2071 reflection nebula in the Orion B region. This
cluster is of interest because it is one of the closest regions known to harbor
embedded high-mass stars. We report the discovery of hard X-ray emission from
the dense ... | 0612563v1 |
2006-12-21 | Rotating Collapse of Stellar Iron Cores in General Relativity | We present results from the first 2+1 and 3+1 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 full 3+1 and conformally-flat
spacetime evolution methods and find t... | 0612638v2 |
2007-02-13 | A Common Explosion Mechanism for Type Ia Supernovae | Type Ia supernovae, the thermonuclear explosions of white dwarf stars
composed of carbon and oxygen, were instrumental as distance indicators in
establishing the acceleration of the universe's expansion. However, the physics
of the explosion are debated. Here we report a systematic spectral analysis of
a large sample o... | 0702351v1 |
1996-03-21 | Density Matrix Functional Calculations for Matter in Strong Magnetic Fields: I. Atomic Properties | We report on a numerical study of the density matrix functional introduced by
Lieb, Solovej and Yngvason for the investigation of heavy atoms in high
magnetic fields. This functional describes {\em exactly} the quantum mechanical
ground state of atoms and ions in the limit when the nuclear charge $Z$ and the
electron n... | 9603005v1 |
1995-10-25 | First Principles LCGO Calculation of the Magneto-optical Properties of Nickel and Iron | We report a first principles, self-consistent, all electron, linear
combination of Gaussian orbitals (LCGO) calculation of a comprehensive
collection of magneto-optical properties of nickel and iron based on density
functional theory. Among the many magneto-optical effects, we have studied the
equatorial Kerr effect fo... | 9510148v1 |
1996-06-05 | Multiple-Scattering Theory of X-Ray Magnetic Circular Dichroism: Implementation and Results for Iron K-edge | An implementation of the multiple-scattering approach to x-ray magnetic
circular dichroism (XMCD) in K-edge x-ray absorption spectroscopy is presented.
The convergence problems due to the cluster size and the relativistic
corrections are solved using an expansion of the Dirac Green function for
complex energies up to t... | 9606022v1 |
1998-08-10 | LDA++ approach to electronic structure of magnets: correlation effects in iron | A novel approach to investigation of correlation effects in the electronic
structure of magnetic crystals which takes into account a frequency dependence
of the self energy (so called ``LDA++ approach'') is developed. The fluctuation
exchange approximation is generalized to the spin-polarized multi-band case and
its lo... | 9808094v1 |
1999-08-20 | Density-functional-theory calculations of molecular nitrogen on ruthenium cluster | Density-functional-theory calculations for the adsorption of molecular
nitrogen on ruthenium surface are reported. It is found that nitrogen molecule
is adsorbed while standing perpendicular to the triangular surface of
ruthenium. The doping by K atoms favours the adsorption of molecular nitrogen.
The calculation of th... | 9908300v1 |
1999-08-27 | Thermodynamics of hexagonal-close-packed iron under Earth's core conditions | The free energy and other thermodynamic properties of hexagonal-close-packed
iron are calculated by direct {\em ab initio} methods over a wide range of
pressures and temperatures relevant to the Earth's core. The {\em ab initio}
calculations are based on density-functional theory in the generalised-gradient
approximati... | 9908400v1 |
2000-01-05 | Circularly polarized light emission in scanning tunneling microscopy of magnetic systems | Light is produced when a scanning tunneling microscope is used to probe a
metal surface. Recent experiments on cobalt utilizing a tungsten tip found that
the light is circularly polarized; the sense of circular polarization depends
on the direction of the sample magnetization, and the degree of polarization is
of order... | 0001044v1 |
2000-02-14 | Thermodynamic stability of Fe/O solid solution at inner-core conditions | We present a new technique which allows the fully {\em ab initio} calculation
of the chemical potential of a substitutional impurity in a high-temperature
crystal, including harmonic and anharmonic lattice vibrations. The technique
uses the combination of thermodynamic integration and reference models
developed recentl... | 0002208v1 |
2001-07-09 | On the Magnetism of the Normal State in MgB2 | The experimentally observed ferromagnetism in MgB2 in the normal state is
attributed to micro phase separated inclusions of iron. This magnetic character
is also observed when the iron content of the samples is reduced below 20
micro-g/g, however in these samples the diamagnetism of MgB2 is apparent and is
measured. It... | 0107169v3 |
2001-10-01 | Importance of Magnetism in Phase Stability, Equations of State, and Elasticity | The effects of magnetism on high pressure properties of transition metals and
transition metal compounds can be quite important. In the case of Fe, magnetism
is responsible for stability of the body-centered cubic (bcc) phase at ambient
conditions, and the large thermal expansivity in face-centered cubic (fcc)
iron, an... | 0110025v5 |
2001-11-14 | Interlayer exchange coupling and giant magnetoresistance in Fe/V (001) superlattices | Magnetization and magnetoresistivity studies of Fe/V (001) superlattices are
reported. The first giant magnetoresistance peak with respect to the vanadium
and iron layer thicknesses is investigated. The interlayer antiferromagnetic
coupling strength is found to show a peak at a vanadium layer thickness of
13 atomic m... | 0111255v1 |
2002-05-13 | Direct visualization of iron sheath shielding effect in MgB_2 superconducting wires | Local magneto-optical imaging and global magnetization measurement techniques
were used in order to visualize shielding effects in the superconducting core
of MgB_2 wires sheathed by ferromagnetic iron (Fe). The magnetic shielding can
provide a Meissner-like state in the superconducting core in applied magnetic
fields ... | 0205253v2 |
2002-05-27 | Superconductivity of epsilon-Fe: complete resistive transition | Last year, iron was reported to become superconducting at temperatures below
2K and pressures between 15 and 30 GPa. The evidence presented was a weak
resistivity drop, suppressed by a magnetic field above 0.2 T, and a small
Meissner signal. However, a compelling demonstration, such as the occurrence of
zero resistance... | 0205557v1 |
2003-05-16 | Avoiding quenching in superconducting rings | A procedure for avoiding the quenching associated to a previously reported
method for inducing currents in superconducting rings [H. Gonzalez-Jorge et
al., Appl. Phys. Lett. 81, 4207 (2002)] is proposed. High persistent currents
are induced in two textured YBCO rings (1536 and 2870 A) using a modified
version of the or... | 0305392v1 |
2003-06-17 | Electron Spectroscopy and Density-Functional Study of "Ferric Wheel" Molecules | The Li-centered "ferric wheel" molecules with six oxo-bridged iron atoms form
molecular crystals. We probed their electronic structure by X-ray photoelectron
(XPS) and soft X-ray emission spectroscopy (XES), having calculated in parallel
the electronic structure of a single "ferric wheel" molecule from
first-principles... | 0306430v1 |
2004-01-21 | Ab initio investigation of structural and magnetic properties of Fe|ZnSe(001) | We investigate 1, 2, 3, and 4 monolayers of iron grown on the (001) surface
of ZnSe using spin density functional theory, plane-wave expansion, and
ultrasoft pseudopotentials. An ideal structure of the interface is plausible
due to the very small lattice mismatch between both materials. However, we
observe dramatic dev... | 0401388v1 |
2004-03-09 | Room temperature study of a strain-induced electronic superstructure on a magnetite (111) surface | A magnetite (Fe3O4) single crystal (111) surface has been studied at various
oxygen-iron surface stoichiometries. The stoichiometry was modified by
controlling the in-situ sample anneal conditions. We have found the conditions
that lead to the formation of an oxygen-rich surface that forms a
quasi-hexagonal superstruct... | 0403238v1 |
2004-03-18 | Overcritical state in superconducting round wires sheathed by iron | Magnetic measurements carried out on MgB_2 superconducting round wires have
shown that the critical current density J_c(B_a) in wires sheathed by iron can
be significantly higher than that in the same bare (unsheathed) wires over a
wide applied magnetic field B_a range. The magnetic behavior is, however,
strongly depen... | 0403454v1 |
2004-11-08 | High-frequency electron paramagnetic resonance investigation of the Fe3+ impurity center in polycrystalline PbTiO3 in its ferroelectric phase | The intrinsic iron(III) impurity center in polycrystalline lead titanate was
investigated by means of high-frequency electron paramagnetic resonance (EPR)
spectroscopy in order to determine the local-environment sensitive fine
structure parameter D. At a spectrometer frequency of 190 GHz, spectral
analysis of a powder ... | 0411167v1 |
2004-12-23 | Nanocrystallization and Amorphization Induced by Reactive Nitrogen Sputtering in Iron and Permalloy | Thin films of iron and permalloy Ni80Fe20 were prepared using an Ar+N2
mixture with magnetron sputtering technique at ambient temperature. The
nitrogen partial pressure, during sputtering process was varied in the range of
0 to 100%, keeping the total gas flow at constant. At lower nitrogen pressures
RN2<33% both Fe an... | 0412657v1 |
2005-01-25 | Fermi Surface and Electron Correlation Effects of Ferromagnetic Iron | The electronic band structure of bulk ferromagnetic iron is explored by
angle-resolved photoemission for electron correlation effects. Fermi surface
cross-sections as well as band maps are contrasted with density functional
calculations. The Fermi vectors and band parameters obtained from photoemission
and their predic... | 0501585v1 |
2005-01-28 | Spin waves in paramagnetic BCC iron: spin dynamics simulations | Large scale computer simulations are used to elucidate a longstanding
controversy regarding the existence, or otherwise, of spin waves in
paramagnetic BCC iron. Spin dynamics simulations of the dynamic structure
factor of a Heisenberg model of Fe with first principles interactions reveal
that well defined peaks persist... | 0501713v1 |
2005-03-11 | Ambipolar Cu- and Fe-Phthalocyanine single-crystal field-effect transistors | We report the observation of ambipolar transport in field-effect transistors
fabricated on single crystals of Copper- and Iron-Phthalocyanine, using gold as
a high work-function metal for the fabrication of source and drain electrodes.
In these devices, the room-temperature mobility of holes reaches 0.3 cm$^2$/Vs
in bo... | 0503282v1 |
2005-08-03 | Comparative study of the catalytic growth of patterned carbon nanotube films | Three different catalysts (Fe, Ni, Co nitrates dissolved in ethanol) were
patterned on a SiO2/Si substrate and multi-wall carbon nanotubes were grown by
catalytic decomposition of acetylene. We compare the growth of the carbon
nanostructures in the temperature range between 580C and 1000C. With our
experimental set-up ... | 0508112v2 |
2005-12-19 | Lattice dynamics and thermodynamics of bcc iron at pressure: first-principles linear response study | We compute the lattice-dynamical and thermal equation of state properties of
ferromagnetic bcc iron using the first principles linear response
linear-muffin-tin-orbital method in the generalized-gradient approximation. The
calculated phonon dispersion and phonon density of states, both at ambient and
high pressures, sh... | 0512469v1 |
2006-07-30 | Molecular Dynamics Study of the Catalyst Particle Size Dependence on Carbon Nanotube Growth | The molecular dynamics method, based on an empirical potential energy
surface, was used to study the effect of catalyst particle size on the growth
mechanism and structure of single-walled carbon nanotubes (SWNTs). The
temperature for nanotube nucleation (800-1100 K), which occurs on the surface
of the cluster, is simi... | 0607800v1 |
2006-08-29 | ODMR Of Impurity Centers Embedded In Silicon Microcavities | We present the findings of high efficient light absorption in self-assembled
quantum wells (SQW) embedded in silicon microcavities that exhibit a
distributed feedback identified by the FIR transmission spectra. The excitonic
normal-mode coupling (NMC) is found to result in high efficient bound exciton
photoluminescence... | 0608630v1 |
2006-08-29 | Iron-Based Heavy Quasiparticles in SrFe$_{4}$Sb$_{12}$: An Infrared Spectroscopic Study | Temperature-dependent infrared reflectivity spectra of SrFe$_{4}$Sb$_{12}$
has been measured. A renormalized Drude peak with a heavy effective mass and a
pronounced pseudogap of 10 meV develops in the optical conductivity spectra at
low temperatures. As the temperature decreases below 100 K, the effective mass
($m^{*}$... | 0608637v1 |
2006-09-07 | The Evolution of Magnetism in Iron from the Atom to the Bulk | The evolution of the magnetic moment in iron clusters containing 20 to 400
atoms is investigated using first-principles numerical calculations based on
density-functional theory and real-space pseudopotentials. Three families of
clusters are studied, characterized by the arrangement of atoms: icosahedral,
body-centered... | 0609154v1 |
2006-10-12 | Effect of the Fe substitution in Ti-Ni shape memory alloys | Shape memory Ti-Ni alloys attracted much attention in the recent years, since
they are shape memory, intelligent as well as functional materials. In the
present investigation Ti51Ni49 and Ti51Ni45Fe4 alloys were synthesized through
radio frequency (RF) induction melting. The alloy was characterized through
x-ray diffra... | 0610340v1 |
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