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2023-05-24 | Modeling the chemical enrichment history of the Bulge Fossil Fragment Terzan 5 | Terzan 5 is a heavily obscured stellar system located in the inner Galaxy. It
has been postulated to be a stellar relic, a Bulge Fossil Fragment witnessing
the complex history of the assembly of the Milky Way bulge. In this paper, we
follow the chemical enrichment of a set of putative progenitors of Terzan 5 to
assess ... | 2305.15355v1 |
2023-06-07 | 2021 occultations and transits of Linus orbiting (22) Kalliope: I. Polygonal and `cliptracing' algorithm | The satellite Linus orbiting the main-belt asteroid (22) Kalliope exhibited
occultation and transit events in late 2021. A photometric campaign was
organized and observations were taken by the TRAPPIST-South, SPECULOOS-Artemis,
OWL-Net, and BOAO telescopes, with the goal to constrain models of this system.
Our dynamica... | 2306.04768v1 |
2023-07-04 | Packed bed thermal energy storage for waste heat recovery in the iron and steel industry: An experimental study on powder hold-up and pressure drop | Waste heat recovery in the energy intensive industry is one of the most
important measures for the mitigation of climate change. The utilization of
just a fraction of the theoretically available waste heat potential would lead
to a significant reduction of the primary energy consumption and hence a
reduction of greenho... | 2307.01585v2 |
2023-07-10 | The individual abundance distributions of disc stars across birth radii in GALAH | Individual abundances in the Milky Way disc record stellar birth properties
(e.g. age, birth radius ($R_{\rm birth}$)) and capture the diversity of the
star-forming environments over time. Assuming an analytical relationship
between ([Fe/H], [$\alpha$/Fe]) and $R_{\rm birth}$, we examine the
distributions of individual... | 2307.04724v1 |
2023-07-11 | Dynamics of orbital degrees of freedom probed via isotope $^{121,123}$ Sb nuclear quadrupole moments in Sb-substituted iron-pnictide superconductors | Isotope $^{121,123}$Sb nuclei with large electric quadrupole moments are
applied to investigate the dynamics of orbital degrees of freedom in
Sb-substituted iron(Fe)-based compounds. In the parent compound
LaFe(As$_{0.6}$Sb$_{0.4}$)O, the nuclear spin relaxation rate
$^{121,123}(T_{1}^{-1})$ at $^{121,123}$Sb sites was... | 2307.05112v1 |
2023-07-11 | The Dependence of Iron-rich Metal-poor Star Occurrence on Galactic Environment Supports an Origin in Thermonuclear Supernova Nucleosynthesis | It has been suggested that a class of chemically peculiar metal-poor stars
called iron-rich metal-poor (IRMP) stars formed from molecular cores with metal
contents dominated by thermonuclear supernova nucleosynthesis. If this
interpretation is accurate, then IRMP stars should be more common in
environments where thermo... | 2307.05669v2 |
2023-07-31 | Effects of Grain Magnetic Properties and Grain Growth on Synthetic Dust Polarization of MHD Simulations in Protostellar Environments | Thermal dust polarization is a powerful tool to probe magnetic fields
($\textbf{B}$) and grain properties. However, a systematic study of the
dependence of dust polarization on grain properties in protostellar
environments is not yet available. In this paper, we post-process a non-ideal
MHD simulation of a collapsing p... | 2307.16829v2 |
2023-08-02 | Numerical modeling of thermal dust polarization from aligned grains in the envelope of evolved stars with updated POLARIS | Magnetic fields are thought to influence the formation and evolution of
evolved star envelopes. Thermal dust polarization from magnetically aligned
grains is potentially a powerful tool for probing magnetic fields and dust
properties in these circumstellar environments. In this paper, we present
numerical modeling of t... | 2308.01215v1 |
2023-08-02 | Oxygen, sulfur, and iron radial abundance gradients of classical Cepheids across the Galactic thin disk | Classical Cepheids (CCs) are solid distance indicators and tracers of young
stellar populations. Our aim is to provide iron, oxygen, and sulfur abundances
for the largest and most homogeneous sample of Galactic CCs ever analyzed. The
current sample covers a wide range in Galactocentric distances (RG), pulsation
modes a... | 2308.01928v1 |
2023-08-29 | Planet formation throughout the Milky Way: Planet populations in the context of Galactic chemical evolution | As stellar compositions evolve over time in the Milky Way, so will the
resulting planet populations. In order to place planet formation in the context
of Galactic chemical evolution, we make use of a large ($N = 5\,325$) stellar
sample representing the thin and thick discs, defined chemically, and the halo,
and we simu... | 2308.15504v1 |
2023-09-11 | The Scale of Stellar Yields: Implications of the Measured Mean Iron Yield of Core Collapse Supernovae | The scale of alpha-element yields is difficult to predict from theory because
of uncertainties in massive star evolution, supernova physics, and black hole
formation, and it is difficult to constrain empirically because the impact of
higher yields can be compensated by greater metal loss in galactic winds. We
use a rec... | 2309.05719v1 |
2023-10-11 | Absence of topological Hall effect in Fe$_x$Rh$_{100-x}$ epitaxial films: revisiting their phase diagram | A series of Fe$_x$Rh$_{100-x}$ ($30 \leq x \leq 57$) films were epitaxially
grown using magnetron sputtering, and were systematically studied by
magnetization-, electrical resistivity-, and Hall resistivity measurements.
After optimizing the growth conditions, phase-pure Fe$_{x}$Rh$_{100-x}$ films
were obtained, and th... | 2310.07140v1 |
2023-10-19 | Potential Lifshitz transition at optimal substitution in nematic pnictide Ba$_{1-x}$Sr$_x$Ni$_2$As$_2$ | BaNi$_2$As$_2$ is a structural analog of the pnictide superconductor
BaFe$_2$As$_2$, which, like the iron-based superconductors, hosts a variety of
ordered phases including charge density waves (CDWs), electronic nematicity,
and superconductivity. Upon isovalent Sr substitution on the Ba site, the
charge and nematic or... | 2310.13163v1 |
2023-10-31 | First spectroscopic investigation of Anomalous Cepheid variables | Anomalous Cepheids (ACEPs) are intermediate mass metal-poor pulsators mostly
discovered in dwarf galaxies of the Local Group. However, recent Galactic
surveys, including the Gaia DR3, found a few hundreds of ACEPs in the Milky
Way. Their origin is not well understood. We aim to investigate the origin and
evolution of G... | 2310.20503v1 |
2023-11-08 | A self-synthesized origin of heavy metals in hot subdwarf stars? | Some He-rich hot subdwarf stars (He-sdOBs) present high abundances of
trans-iron elements, such as Sr, Y, Zr and Pb. Diffusion processes are
important in hot subdwarf stars, and it is thought that the high abundances of
heavy elements in these stars are due to the action of radiative levitation.
However, during the for... | 2311.04700v1 |
2023-12-07 | Interface-Induced Superconductivity in Magnetic Topological Insulator-Iron Chalcogenide Heterostructures | When two different electronic materials are brought together, the resultant
interface often shows unexpected quantum phenomena, including interfacial
superconductivity and Fu-Kane topological superconductivity (TSC). Here, we use
molecular beam epitaxy (MBE) to synthesize heterostructures formed by stacking
together tw... | 2312.04353v1 |
2023-12-08 | The Heavy Metal Survey: The Evolution of Stellar Metallicities, Abundance Ratios, and Ages of Massive Quiescent Galaxies Since z~2 | We present the elemental abundances and ages of 19 massive quiescent galaxies
at $z\sim1.4$ and $z\sim2.1$ from the Keck Heavy Metal Survey. The ultra-deep
LRIS and MOSFIRE spectra were modeled using a full-spectrum stellar population
fitting code with variable abundance patterns. The galaxies have iron
abundances betw... | 2312.05307v1 |
2023-12-12 | Abundances of iron-peak elements in accreted and in situ born Galactic halo stars | Previous work on the abundances of C, O, Na, Mg, Si, Ca, Ti, Cr, Mn, Fe, Ni,
Cu, and Zn in low-alpha (accreted) and high-alpha (in situ born) halo stars is
extended to include the abundances of Sc, V, and Co, enabling us to study the
nucleosynthesis of all iron-peak elements along with the lighter elements. The
Sc, V, ... | 2312.07768v1 |
2023-12-20 | On the Origin of the X-ray Emission in Heavily Obscured Compact Radio Sources | X-ray continuum emission of active galactic nuclei (AGNs) may be reflected by
circumnuclear dusty tori, producing prominent fluorescence iron lines at X-ray
frequencies. Here we discuss the broad-band emission of three radio-loud AGN
belonging to the class of compact symmetric objects (CSOs), with detected
narrow Fe\,K... | 2312.13418v2 |
2024-01-10 | Nematic quantum disordered state in FeSe | The unusual quantum-disordered magnetic ground state intertwined with
superconductivity and electronic nematicity in FeSe has been a research focus
in iron-based superconductors. However, the intrinsic spin excitations across
the entire Brillouin zone in detwinned FeSe, which forms the basis for a
microscopic understan... | 2401.05092v1 |
2024-01-17 | Aperture and Resolution Effects on Ultraviolet Star-Forming Properties: Insights from Local Galaxies and Implications for High-Redshift Observations | We present an analysis of the effects of spectral resolution and aperture
scales on derived galaxy properties using far-ultraviolet (FUV) spectra of
local star-forming galaxies from the International Ultraviolet Explorer (R~250,
FOV~10"x20") and Cosmic Origins Spectrograph on the Hubble Space Telescope
(R~15,000, FOV~2... | 2401.08971v1 |
2024-02-09 | High-Resolution X-Ray Spectroscopy of Interstellar Iron Toward Cygnus X-1 and GX 339-4 | We present a high-resolution spectral study of Fe L-shell extinction by the
diffuse interstellar medium (ISM) in the direction of the X-ray binaries Cygnus
X-1 and GX 339-4, using the XMM-Newton reflection grating spectrometer. The
majority of interstellar Fe is suspected to condense into dust grains in the
diffuse ISM... | 2402.06726v1 |
2024-02-28 | Elastocaloric evidence for a multicomponent superconductor stabilized within the nematic state in Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ | The iron-based high-$T_c$ superconductors exhibit rich phase diagrams with
intertwined phases, including magnetism, nematicity and superconductivity. The
superconducting $T_c$ in many of these materials is maximized in the regime of
strong nematic fluctuations, making the role of nematicity in influencing the
supercond... | 2402.17945v1 |
2024-02-28 | METAL-Z: Measuring dust depletion in low metalicity dwarf galaxies | The cycling of metals between interstellar gas and dust is a critical aspect
of the baryon cycle of galaxies, yet our understanding of this process is
limited. This study focuses on understanding dust depletion effects in the low
metallicity regime (< 20% Zo) typical of cosmic noon. Using medium-resolution
UV spectrosc... | 2402.18733v1 |
2024-03-07 | Effects of mechanical stress, chemical potential, and coverage on hydrogen solubility during hydrogen enhanced decohesion of ferritic steel grain boundaries: A first-principles study | Hydrogen enhanced decohesion (HEDE) is one of the many mechanisms of hydrogen
embrittlement, a phenomenon which severely impacts structural materials such as
iron and iron alloys. Grain boundaries (GBs) play a critical role in this
mechanism, where they can provide trapping sites or act as hydrogen diffusion
pathways. ... | 2403.04741v1 |
2024-03-20 | A Gap in the Densities of Small Planets Orbiting M Dwarfs: Rigorous Statistical Confirmation Using the Open-source Code RhoPop | Using mass-radius-composition models, small planets ($\mathrm{R}\lesssim 2
\mathrm{R_\oplus}$) are typically classified into three types: iron-rich,
nominally Earth-like, and those with solid/liquid water and/or atmosphere.
These classes are generally expected to be variations within a compositional
continuum. Recently... | 2403.13961v1 |
1993-04-06 | Element Diffusion in the Solar Interior | We study the diffusion of helium and other heavy elements in the solar
interior by solving exactly the set of flow equations developed by Burgers for
a multi-component fluid, including the residual heat-flow terms. No
approximation is made concerning the relative concentrations and no restriction
is placed on the numbe... | 9304005v1 |
1994-04-20 | Analysis of the 3d6 4s(6D)4f-5g Supermultiplet of Fe I in Laboratory and Solar Infrared Spectra | The combined laboratory and solar analysis of the highly-excited
subconfigurations 4f and 5g of Fe I has allowed us to classify 87 lines of the
4f-5g supermultiplet in the spectral region 2545-2585 cm-1. The level structure
of these JK-coupled configurations is predicted by semiempirical calculations
and the quadrupoli... | 9404050v1 |
1995-03-03 | The First Second of a Type-II Supernova: Convection, Accretion, and Shock Propagation | One- and two-dimensional hydrodynamical simulations of neutrino-driven
supernova explosions are discussed. The simulations cover the phase between the
stagnation of the prompt shock and about one second after core bounce.
Systematic variation of the neutrino fluxes from the neutrino sphere shows that
the explosion ener... | 9503015v1 |
1995-04-03 | COOLING FLOW MODELS OF THE X--RAY EMISSION AND TEMPERATURE PROFILES FOR A SAMPLE OF ELLIPTICAL GALAXIES | A simple spherically-symmetric, steady-state, cooling-flow description with
gas loss (following Sarazin \& Ashe 1989), within galaxy models constrained by
radially extended stellar dynamical data, is shown to provide generally
reasonable fits to the existing data on X-ray emission profiles and
temperatures for a set of... | 9504002v2 |
1995-05-18 | X-RAY OUTBURST OF THE PECULIAR SEYFERT GALAXY IC 3599 | We report optical, soft X-ray, and UV observations of the peculiar Seyfert
galaxy IC 3599 using data obtained with ROSAT and IUE. Most remarkably, we
discovered a rapid decrease of the X-ray flux by a factor of about 100 within
one year and a more gradual decrease thereafter. The X-ray spectrum of IC 3599
was soft at f... | 9505085v1 |
1995-10-19 | Model Atmospheres for Low Field Neutron Stars | We compute model atmospheres and emergent spectra for low field (B<10^10 G)
neutron stars, using new opacity and equation of state data from the OPAL
project. These computations, incorporating improved treatments of flux
transport and convective stability, provide spectra for hydrogen, solar
abundance and iron atmosphe... | 9510094v2 |
1995-11-22 | Metal Enhancements in the X-ray Gas around Central Cluster Galaxies | The X-ray emission by hot gas around the central galaxies of galaxy clusters
is commonly modeled assuming the existence of steady-state, multiphase cooling
flows. The inflowing gas will be chemically enriched by type Ia supernovae and
stellar mass loss occurring in the outer parts of the central galaxy. This may
give r... | 9511105v1 |
1995-12-12 | The first simultaneous X-ray/gamma-ray observations of Cyg X-1 by Ginga and OSSE | We present the results of 4 simultaneous observations of Cygnus X-1 by Ginga
and OSSE. The X-ray/gamma-ray spectra can be described by an intrinsic
continuum and a component due to Compton reflection including an iron K-alpha
line. The intrinsic spectrum at X-ray energies is a power-law with a photon
spectral index of ... | 9512073v1 |
1996-05-10 | The Compton Mirror in NGC 4151 | We show that the sharp cutoff in the hard X-ray spectrum of NGC 4151, unusual
for Seyfert 1 galaxies, can be reconciled with the average Seyfert 1 spectrum
if we assume that the central source is completely hidden from our line of
sight by the thick part of the accretion disk or by the broad emission line
clouds. The o... | 9605052v1 |
1996-07-08 | Physical Conditions in Low Ionization Regions of the Orion Nebula | We reexamine the spectroscopic underpinnings of recent suggestions that [O I]
and [Fe II] lines from the Orion H II region are produced in gas where the
iron-carrying grains have been destroyed and the electron density is
surprisingly high. Our new observations show that previous detections of [O I]
5577 were dominated... | 9607045v1 |
1996-08-19 | Scattering of X-ray emission lines by the neutral and molecular hydrogen in the Sun's atmosphere and in the vicinity of active galactic nuclei and compact sources | In many astrophysical objects an account for scattering of the X-ray
fluorescent and resonance lines of iron ions by the electrons, bound in atomic
and molecular hydrogen is important. Specific distortions of the scattered line
profile spectrum appear in comparison with scattering by free electrons.
Analysis of scatter... | 9608114v1 |
1996-10-09 | Galaxy evolution: the effect of dark matter on the chemical evolution of ellipticals and galaxy clusters | In this paper we discuss the chemical evolution of elliptical galaxies and
its consequences on the evolution of the intracluster medium (ICM). We use
chemical evolution models taking into account dark matter halos and compare the
results with previous models where dark matter was not considered. In
particular, we exami... | 9610059v1 |
1996-10-11 | Spallation of Iron in Black Hole Accretion Flows | In the local Galactic interstellar medium there is approximate energy
equipartition between cosmic rays, magnetic fields and radiation. If this holds
in the central regions of AGN, in particular Seyfert galaxies, then consideral
nuclear spallation of Fe occurs, resulting in enhanced abundances of the sub-Fe
elements Ti... | 9610081v1 |
1996-10-29 | Comment on a paper by M. A. Bautista ``Atomic data from the Iron Project. XVI. Photoionization cross sections and oscillator strengths for Fe V'' | Recently, Bautista (1996, A&AS, 119, 105) reported new calculations of
photoionization cross sections for Fe V, and compared them with the earlier
results of Reilman & Manson (1979, ApJS, 40, 815) and Verner et al. (1993,
Atomic Data Nucl. Data Tables, 55, 233). Bautista claimed that beyond 10 Ry the
new cross sections... | 9610244v1 |
1996-11-13 | Galactic Drips and How to Stop Them! | The temperature of hot interstellar gas at large radii in elliptical galaxies
can be lower than the mean galactic virial temperature. If so, a nonlinear
cooling wave can form in the hot interstellar gas and propagate slowly toward
the galactic core. If the cooling wave survives hydrodynamic instabilities, it
can interm... | 9611096v1 |
1996-11-29 | Ultraviolet Light from Old Stellar Populations | We consider the general theoretical problem of ultraviolet light from old
stellar populations (t > 2 Gyr), and the interpretation of galaxy spectra at
short wavelengths (lamda < 3200A) The sources believed to be responsible for
the observed `ultraviolet upturn phenomenon' (UVX) are Post-AGB (P-AGB),
extreme horizontal ... | 9612008v1 |
1996-12-19 | The Great Annihilator 1E1740.7-2942: Molecular cloud connection and coronal structure | Using 12CO and 13CO observations we present column density maps of the
molecular cloud (V = -135 km/s) in the direction of 1E1740.7-2942. Hydrogen
column densities of the cloud scatter between (3.5 - 11) 10**22 cm-2, depending
on the method used. From this we conclude, deriving first a simple analytic
formula, that des... | 9612194v1 |
1997-01-08 | The ASCA X-ray spectrum of the powerful radio galaxy 3C109 | We report the results from an ASCA X-ray observation of the powerful Broad
Line Radio Galaxy, 3C109. The ASCA spectra confirm our earlier ROSAT detection
of intrinsic X-ray absorption associated with the source. The absorbing
material obscures a central engine of quasar-like luminosity. The luminosity is
variable, havi... | 9701033v1 |
1997-01-22 | General relativistic effects in the neutrino-driven wind and r-process nucleosynthesis | We discuss general relativistic effects in the steady-state neutrino-driven
``wind'' which may arise from nascent neutron stars. In particular, we
generalize previous analytic estimates of the entropy per baryon $S$, the mass
outflow rate $\dot M$, and the dynamical expansion time scale $\tau_{dyn}$. We
show that $S$ i... | 9701178v1 |
1997-04-18 | Gamma rays and neutrinos from the Crab Nebula produced by pulsar accelerated nuclei | We investigate the consequences of the acceleration of heavy nuclei (e.g.
iron nuclei) by the Crab pulsar. Accelerated nuclei can photodisintegrate in
collisions with soft photons produced in the pulsar's outer gap, injecting
energetic neutrons which decay either inside or outside the Crab Nebula. The
protons from neut... | 9704186v1 |
1997-05-08 | Spectropolarimetry of FIRST 0840+3633 | We present Keck spectropolarimetry of a rare ``Iron Lo-BALQSO,'' FIRST
0840+3633. The continuum is 4% polarized near 2000 angstroms rest-frame, but
falls to 2% at longer wavelengths, and maintains a relatively constant position
angle of 50 degrees. The emission lines are unpolarized. The polarization
increases up to 8%... | 9705053v1 |
1997-05-12 | Physical Conditions of the Coronal Line Region in Seyfert Galaxies | The launch of the Infrared Space Observatory and new atomic data have opened
a window to the study of high ionization gas in active galactic nuclei (AGN).
We present the results of a large number of photoionization simulations of the
``coronal line'' region in AGN, employing new atomic data from the Opacity and
Iron Pr... | 9705082v1 |
1997-06-02 | Decoupled Nuclei and Nuclear Polar Rings in Regular Spiral Galaxies. NGC 2841 | The Sb galaxy NGC 2841 was observed at the 6 m telescope of SAO RAS with the
Multi-Pupil Field Spectrograph and at the 1 m telescope of SAO RAS with the
long-slit spectrograph. An unresolved nucleus of NGC 2841 is shown to be
chemically decoupled both in magnesium and in iron with abundance break
estimates of 0.36 dex ... | 9706003v1 |
1997-06-07 | X-ray detections of weak Seyfert2's with BeppoSAX | We report the detection in the X rays of two weak Seyfert2's (NGC3393 and
NGC4941) with the Italian-Dutch satellite BeppoSAX. These are among the first
sources observed in a sample of 12 Seyfert2's which are being studied within
the BeppoSAX core program, in an effort to probe the putative torus at high
X-ray energies,... | 9706070v1 |
1997-07-08 | Detailed NLTE Model Atmospheres for Novae during Outburst: I. New Theoretical Results | We present new detailed NLTE calculations for model atmospheres of novae
during outburst. This fully self-consistent NLTE treatment for a number of
model atoms includes 3922 NLTE levels and 47061 NLTE primary transitions. We
discuss the implication of departures from LTE for the strengths of the lines
in nova spectra. ... | 9707104v1 |
1997-07-22 | Spectropolarimetry of FIRST BAL QSOs | We present Keck spectropolarimetry of two rare low-ionization broad
absorption line (BAL) QSOs, FIRST J084044.5+363328 and FIRST J155633.8+351758,
that also exhibit narrow absorption lines from metastable excited levels of Fe
II (``Iron Lo-BALs''). These QSOs were discovered in optical follow-ups to a
deep radio survey... | 9707238v1 |
1997-07-22 | A Second UV "Light Bulb" behind the SN 1006 Remnant | A point X-ray source located 9 arcmin northeast of the center of SN~1006 has
been spectroscopically identified as a background QSO, with a redshift of
0.335. The object is moderately bright, with magnitude V=18.3. If its
ultraviolet spectrum is typical of low-z quasars, this object will be a second
(after the Schweizer... | 9707247v1 |
1997-08-25 | ASCA observations of type-2 Seyfert Galaxies. III. Orientation and X-ray Absorption | We discuss the spectral properties of a sample of type-2 Seyfert galaxies
based upon the analysis of \asca data. In this paper we consider the sources
for which the X-ray spectra appear to be dominated by the nuclear continuum,
transmitted through a large column of absorbing material. We find that both
Seyfert-2 galaxi... | 9708231v1 |
1997-09-02 | New Measurement of Metal Abundance in the Elliptical Galaxy NGC 4636 with Asca | High quality X-ray spectra of NGC 4636 are obtained with ASCA. Theoretical
models are found unable to reproduce the data in the Fe-L line region. Spectral
data above 1.4 keV indicate that Mg to Si abundance ratio is $\sim 1$ solar.
Assuming that the abundance ratios among $\alpha$-elements are the same with
the solar r... | 9709009v1 |
1997-09-22 | Discovery of a Large-Scale Abundance Gradient in the Cluster of Galaxies AWM7 with ASCA | A large-scale gradient in the metal abundance has been detected with ASCA
from an X-ray bright cluster of galaxies AWM7. The metal abundance shows a peak
of 0.5 solar at the center and smoothly declines to <~ 0.2 solar at a radius of
500 kpc. The gas temperature is found to be constant at 3.8 keV. The radial
distributi... | 9709208v1 |
1997-10-17 | The IntraCluster Medium: An Invariant Stellar IMF | Evidence supporting the hypothesis of an invariant stellar Initial Mass
Function is strong and varied. The intra-cluster medium in rich clusters of
galaxies is one of the few contrary locations where recent interpretations of
the chemical abundances have favoured an IMF that is biased towards massive
stars, compared to... | 9710195v1 |
1997-11-14 | Cygnus X-1: X-ray Emission Mechanism and Geometry | We summarize recent observations of Cyg X-1 during its 1996 state transition.
The results favor an emission geometry with a central optically thin corona
surrounded by an optically thick, geometrically thin accretion disk. As the
soft state is approached, the inner edge of the disk moves closer to the black
hole, and t... | 9711166v1 |
1997-11-19 | Line emission from an accretion disk around black hole: effects of the disk structure | The observed iron K-alpha fluorescence lines in Seyfert galaxies provide
strong evidence for an accretion disk near a supermassive black hole as a
source of the line emission. Previous studies of line emission have considered
only geometrically thin disks, where the gas moves along geodesics in the
equatorial plane of ... | 9711214v1 |
1997-11-20 | High Energy Break and Reflection Features in the Seyfert Galaxy MCG+8-11-11 | We present the results from ASCA and OSSE simultaneous observations of the
Seyfert 1.5 galaxy MCG+8-11-11 performed in August-September 1995. The ASCA
observations indicate a modest flux increase (20%) in 3 days, possibly
correlated to a softening of the 0.6-9 keV spectrum. The spectrum is well
described by a hard powe... | 9711242v1 |
1997-11-29 | Wide-Band X-Ray Spectra and Images of the Starburst Galaxy M82 | The ASCA results of the starburst galaxy M82 are presented. The X-rays in the
0.5--10 keV band exhibit a thin thermal spectrum with emission lines from
highly ionized magnesium, silicon, and sulfur, as well as a hard tail extending
to higher than 10keV energy. The soft X-rays are spatially extended, while the
hard X-ra... | 9712002v1 |
1997-12-17 | BeppoSAX observations of 3C 273 | We present preliminary results of BeppoSAX AO1 observations of 3C 273
performed in January 1997. We also present a close comparison with data
obtained during the satellite SVP, in July 1996. On average, the AO1 flux is
about a factor 2 higher than the flux detected during the SVP, and roughly on
the middle of the histo... | 9712234v1 |
1997-12-18 | 1H0419-577: a two-state Seyfert Galaxy? | The preliminary results of the BeppoSAX observation of the radio-quiet AGN
1H0419-577 are presented. Despite its broad line optical spectrum, the
intermediate X-ray spectrum (i.e. 2--10 keV) is flatter than typically observed
in Seyfert 1s and no iron line is significantly detected. Even more
intriguingly, a 1992 ROSAT... | 9712248v1 |
1998-01-27 | A Comparison of Cosmic Ray Composition Measurements at the Highest Energies | In recent years the Fly's Eye and Akeno groups have presented analyses of the
cosmic ray mass composition at energies above 10^17 eV. While the analysis of
the Fly's Eye group points to a likely change in mass composition from heavy to
light at energies above 10^18 eV, the Akeno analysis favours an unchanging
compositi... | 9801260v2 |
1998-02-08 | Can Stellar Yields Accurately Constrain the Upper Limit to the Initial Mass Function? | Recent determinations of the upper mass limit to the local initial mass
function (IMF) claim a value of m(upper)=50+/-10 solar masses, based upon
direct comparisons of the observed oxygen and iron abundances in metal-poor
stars with the predicted stellar yields from Type II supernovae (SNe). An
unappreciated uncertaint... | 9802091v1 |
1998-02-11 | ASCA Measurements of Silicon and Iron Abundances in the Intracluster Medium | We analyzed the ASCA X-ray data of 40 nearby clusters of galaxies, whose
intracluster-medium temperature distributes in the range of 0.9--10 keV. We
measured the Si and Fe abundances of the intracluster medium, spatially
averaging over each cluster, but excluding the central $\sim 0.15 h_{50}^{-1}$
Mpc region in order ... | 9802126v1 |
1998-02-13 | Intracluster Medium Abundances Revisited | We examine the origin of heavy elements in the intracluster medium (ICM) of
galaxy clusters, concentrating upon the roles played by supernovae (SNe) Types
Ia and II. The most accurately determined elemental abundances, Si and Fe,
imply a mild predominance of Type II SNe as the source of ICM Fe, contributing
approximate... | 9802172v1 |
1998-02-26 | ASCA spectroscopy of the luminous infrared galaxy NGC6240: X-ray emission from a starburst and a buried active nucleus | We present an X-ray spectral study of the prototype far-infrared galaxy
NGC6240 from ASCA. The soft X-ray spectrum (below 2 keV) shows clear signatures
of thermal emission well described with a multi-temperature optically-thin
plasma, which probably originates in a powerful starburst. Strong hard X-ray
emission is also... | 9802336v1 |
1998-03-31 | IRAS 06562-0337, The Iron Clad Nebula: A New Young Star Cluster | IRAS 06562-0337 has been the recent subject of a classic debate:
proto-planetary nebula or young stellar object? We present the first 2 micron
image of IRAS 06562-0337, which reveals an extended diffuse nebula containing
approximately 70 stars inside a 30 arcsec radius around a bright, possibly
resolved, central object... | 9803345v1 |
1998-05-06 | Doppler Imaging of Ap Stars | Doppler imaging, a technique which inverts spectral line profile variations
of an Ap star into a two-dimensional abundance maps, provides new observational
constraints on diffusion mechanism in the presence of a global magnetic field.
A programme is presented here with the aim to obtain abundance distributions of
at le... | 9805065v1 |
1998-05-15 | X-ray spectroscopy of the broad line radio galaxy 3C111 | We present an ASCA observation of the broad line radio galaxy 3C111. The
X-ray spectrum is well described by a model consisting of a
photoelectrically-absorbed power-law form. The inferred absorbing column
density is significantly greater than expected on the basis of 21-cm
measurements of Galactic HI. Whilst this may ... | 9805217v1 |
1998-05-26 | The stellar population of the decoupled nucleus in M 31 | The results of a spectroscopic and photometric investigation of the central
region of M 31 are presented. An analysis of absorption-index radial profiles
involving magnesium, calcium, and iron lines has shown that the unresolved
nucleus of M 31 is distinct by its increased metallicity; unexpectedly, among
two nuclei of... | 9805318v1 |
1998-05-29 | Quasi-periodic oscillations discovered in the new X-ray pulsar XTE J1858+034 | We report the discovery of low frequency quasi-periodic oscillations centered
at 0.11 Hz in the newly discovered 221 s X-ray pulsar XTE J1858+034. Among
about 30 known transient X-ray pulsars this is the sixth source in which QPOs
have been observed. If the QPOs are produced because of inhomogeneities in the
accretion ... | 9805366v1 |
1998-06-03 | Heavy obscuration in X-ray weak AGNs | We present observations in the 0.1-100 keV spectral band of 8 Seyfert 2
galaxies, obtained by means of BeppoSAX. These sources were selected according
to their [OIII] optical emission line flux, to avoid biases against obscuration
on the pc scale. All sources were detected. All of them are weak X-ray
emitters, and most... | 9806055v2 |
1998-06-10 | Line Emission from an Accretion Disk around a Black hole: Effects of Disk Structure | The observed iron K-alpha fluorescence lines in Seyfert-1 galaxies provide
strong evidence for an accretion disk near a supermassive black hole as a
source of the line emission. These lines serve as powerful probes for examining
the structure of inner regions of accretion disks. Previous studies of line
emission have c... | 9806134v1 |
1998-06-17 | The hidden X-ray Seyfert nucleus in 3C 273: BeppoSAX results | We present the results of BeppoSAX AO1 Core Program observations of 3C~273
performed in Jan. 1997 and compare them in detail with data obtained during the
satellite Science Verification Phase (SVP), in Jul. 1996. Though a power law is
an acceptable representation of the data in the whole 0.1-200 keV range, there
is ind... | 9806229v2 |
1998-06-22 | A New Dual-Component Photoionization Model for the Narrow Emission-Line Regions in Active Galactic Nuclei | Having found that type 1 Seyfert nuclei have excess [FeVII]6087 emission with
respect to type 2s, Murayama & Taniguchi have proposed that the high-ionization
nuclear emission-line region (HINER) traced by the [FeVII]6087 emission resides
in the inner wall of dusty tori. The covering factor of the torus is usually
large... | 9806287v1 |
1998-07-02 | Contribution of Type Ia and Type II Supernovae for Intra-Cluster Medium Enrichment | The origin of the chemical composition of the intracluster medium (ICM) is
discussed in this paper. In particular, the contribution from Type Ia
supernovae (SNe Ia) to the ICM enrichment is shown to exist by adopting the
fitting formulas which have been used in the analysis of the solar system
abundances. Our analysis ... | 9807022v1 |
1998-07-21 | The swan song: the disappearance of the nucleus of NGC 4051 and the echo of its past glory | BeppoSAX observed the low-luminous Seyfert 1 Galaxy NGC4051 in a ultra-dim
X-ray state. The 2-10 keV flux (1.26 x 10^{-12} erg/cm^2/s) was about 20 times
fainter than its historical average value, and remained steady along the whole
observation (~2.3 days). The observed flat spectrum (\Gamma ~ 0.8) and intense
iron lin... | 9807213v2 |
1998-08-14 | Redshift determination in the X-ray band of gamma-ray bursts | If gamma-ray bursts originate in dense stellar forming regions, the
interstellar material can imprint detectable absorption features on the
observed X-ray spectrum. Such features can be detected by existing and planned
X-ray satellites, as long as the X-ray afterglow is observed after a few
minutes from the burst. If t... | 9808156v1 |
1998-09-04 | Age Dating of a High-Redshift QSO B1422+231 at Z=3.62 and its Cosmological Implications | The observed Fe II(UV+optical)/Mg II lambda lambda 2796,2804 flux ratio from
a gravitationally lensed quasar B1422+231 at z=3.62 is interpreted in terms of
detailed modeling of photoionization and chemical enrichment in the broad-line
region (BLR) of the host galaxy. The delayed iron enrichment by Type Ia
supernovae is... | 9809047v1 |
1998-09-08 | ASCA Observations of the Seyfert 2 Galaxy NGC 7582: An Obscured and Scattered View of the Hidden Nucleus | ASCA observations of the Seyfert 2 galaxy NGC 7582 revealed it was highly
variable on the timescale of $\sim2\times10^4$ s in the hard X-ray (2-10 keV)
band, while the soft X-ray (0.5-2 keV) flux remained constant during the
observations.
The spectral analysis suggests that this object is seen through an obscuring
to... | 9809086v1 |
1998-09-14 | Detection of a cyclotron line and its second harmonic in 4U1907+09 | We report the detection of a cyclotron absorption line and its second
harmonic in the average spectrum of the high mass X-ray binary 4U1907+09
observed by the BeppoSAX satellite on 1997 September 27 and 28. The broad band
spectral capability of BeppoSAX allowed a good determination of the continuum
against which the tw... | 9809167v1 |
1998-09-20 | Emission-Line Probes of Circumnuclear Dust in AGNs | Emission lines that trace elements subject to strong depletion onto grains
provide a means for probing the dust content of AGNs. Examples include infrared
[FeII] and optical [CaII] lines. The excitation mechanisms underlying the
[FeII] lines remain controversial, resulting in related disagreement over the
gas-phase abu... | 9809247v1 |
1998-10-05 | Core Collapse Supernovae --- Theory between Achievements and New Challenges | Multi-dimensional hydrodynamic simulations of the post-bounce evolution of
collapsed stellar iron cores have demonstrated that convective overturn between
the stalled shock and the neutrinosphere can have an important effect on the
neutrino-driven explosion mechanism. Whether a model yields a successful
explosion or no... | 9810058v1 |
1998-10-22 | On the possibility that rotation causes latitudinal abundance variations in stars | The effect of rotation of a star on the distribution of chemical species in
radiative zones is discussed. Gravity darkening generates a large radiative
force on heavy element ions which is directed toward the equatorial plane.
Taking iron as an example, it is shown that this force may produce drift
velocities similar t... | 9810360v1 |
1998-10-22 | Calibrator Design for the COBE Far Infrared Absolute Spectrophotometer (FIRAS) | The photometric errors of the external calibrator for the FIRAS instrument on
the COBE are smaller than the measurement errors on the cosmic microwave
background (CMBR) spectrum (typically 0.02 MJy/sr, 1 sigma), and smaller than
0.01% of the peak brightness of the CMBR. The calibrator is a re-entrant cone,
shaped like ... | 9810373v1 |
1998-11-03 | Microwave Emission by Dust: Mechanisms, Properties and Prospects for ISM Studies | I review my work with Bruce Draine on dust emissivity at microwave
frequencies (3 cm - 3 mm). This emissivity explains the recently detected
"anomalous" component of the galactic foreground emission. Both small (a<0.001
micron) and large grains contribute to this emission. Small grains have
electric dipole moments and ... | 9811043v1 |
1998-11-16 | BeppoSAX confirms extreme relativistic effects in the X-ray spectrum of MCG-6-30-15 | We report the first simultaneous measure of the X-ray broadband (0.1--200
keV) continuum and of the iron K-alpha fluorescent line profile in the Seyfert
1 galaxy MCG-6-30-15. Our data confirms the ASCA detection of a skewed and
redshifted line profile (Tanaka et al. 1995). The most straightforward
explanation is that t... | 9811246v1 |
1998-11-25 | Enrichment of the Intracluster Medium | The relevance of galaxies of different luminosity and mass for the chemical
enrichment of the intracluster medium (ICM) is analysed. For this purpose, I
adopt the composite luminosity function of cluster galaxies from Trentham
(1998), which exhibits a significant rise at the very faint end. The model -
adopting a unive... | 9811409v1 |
1998-12-16 | ASCA Observations of GRO J1744-28 | We report the ASCA results of the bursting X-ray pulsar \gro, which was
observed in February 1996 and March 1997. The source flux in the 2--10 keV band
was $2.0\times10^{-8}$ erg/sec/cm$^2$ in 1996 and $5.0\times10^{-9}$
erg/sec/cm$^2$ in 1997. We detected 12 and 17 Type II bursts during the two
observations with mean ... | 9812298v1 |
1999-01-11 | RXTE Observations of the X-ray Pulsar XTE J1855-026 - a Possible New Supergiant System | A new X-ray source, XTE J1855-026, was discovered during RXTE scans along the
galactic plane. The source shows pulsations at a period of 361 s and also
modulation at a period of 6.1 days which we interpret as the orbital period of
the system. The X-ray spectrum above ~3 keV can be fitted with an absorbed
power law mode... | 9901125v1 |
1999-02-15 | Role of disk galaxies in the chemical enrichment of the intracluster medium | Elliptical galaxies are often assumed to be the primary source of heavy
elements in the intracluster medium (ICM), with the contribution of other
morphological types being negligible. In this paper we argue that a role of
spiral galaxies in the chemical evolution of the ICM is also important. This
statement rests upon ... | 9902202v1 |
1999-02-23 | X-ray reflection spectra from ionized slabs | X-ray reflection spectra are an important component in the X-ray spectra of
many active galactic nuclei and Galactic black hole candidates. It is likely
that reflection takes place from highly ionized surfaces of the accretion disc
in some cases. This can lead to strong Comptonization of the emergent iron, and
other, a... | 9902325v1 |
1999-02-25 | Microwave Emission from Galactic Dust Grains | Observations of the cosmic microwave background have revealed a component of
10-60 GHz emission from the Galaxy which correlates with 100-140um emission
from interstellar dust but has an intensity much greater than expected for the
low-frequency tail of the "electric dipole vibrational" emission peaking at
\~130um. Thi... | 9902356v1 |
1999-03-10 | Heavy nuclei at the end of the cosmic ray spectrum? | We provide an account of the possible acceleration of iron nuclei up to
energies $\sim300$ EeV in the nearby, metally-rich starburst galaxy NGC 253. It
is suggested that particles can escape from the nuclear region with energies of
$\sim10^{15}$ eV and then could be reaccelerated at the terminal shock of the
galactic s... | 9903145v3 |
1999-03-29 | Striking Photospheric Abundance Anomalies in Blue Horizontal-Branch Stars in Globular Cluster M13 | High-resolution optical spectra of thirteen blue horizontal-branch (BHB)
stars in the globular cluster M13 show enormous deviations in element
abundances from the expected cluster metallicity. In the hotter stars (T_eff >
12000 K), helium is depleted by factors of 10 to 100 below solar, while iron is
enhanced to three ... | 9903437v1 |
1999-04-13 | An RXTE Observation of NGC 6300: a new bright Compton reflection Dominated Seyfert 2 Galaxy | Scanning and pointed RXTE observations of the nearby Seyfert 2 galaxy NGC
6300 reveal that it is a source of hard X-ray continuum and large equivalent
width Fe K$\alpha$ emission. These properties are characteristic of
Compton-reflection dominated Seyfert 2 galaxies. The continuum can be modeled
as Compton-reflection; ... | 9904155v1 |
1999-04-14 | Comparison between predicted and empirical DV(Bump -HB) in Galactic Globular Clusters | We present observational estimates of DV(Bump-HB) in a sample of 28 Galactic
Globular Clusters (GGCs) observed by HST. The photometric accuracy and the
sizable number of stars measured in each cluster allowed us to single out the
RGB Bump both in metal-poor and in metal-rich GGCs. Empirical values are
compared with hom... | 9904183v1 |
1999-04-26 | A BeppoSAX observation of the massive X-ray binary 4U1700-37 | A 0.5-200 keV BeppoSAX spectrum of the non-pulsating high-mass X-ray binary
4U1700-37 is presented. The spectrum is well characterized by the standard
accreting pulsar model of an absorbed power-law with a photon index of 1.07
+0.02 -0.03, sharply modified by an exponential cutoff above 5.9 +/- 0.2 keV.
The e-folding e... | 9904349v1 |
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