publicationDate stringlengths 1 2.79k | title stringlengths 1 36.5k ⌀ | abstract stringlengths 1 37.3k ⌀ | id stringlengths 9 47 |
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2004-04-30 | A look with BeppoSAX at the low-luminosity Galactic X-ray source 4U 2206+54 | A pointed observation of the low-luminosity galactic source 4U 2206+54 was
carried out in November 1998 with BeppoSAX. The light curve of 4U 2206+54 shows
erratic variability on a timescale of about 1 hour; neither hardness variations
nor time periodicities are detected throughout this 67 ks long observation.
Thanks to... | 0404603v2 |
2004-05-04 | Galactic Evolution of Nitrogen | We present detailed spectroscopic analysis of nitrogen abundances in 31
unevolved metal-poor stars analysed by spectral synthesis of the near-UV NH
band at 3360 A observed at high resolution with various telescopes. We found
that [N/Fe] scales with that of iron in the metallicity range -3.1 < [Fe/H] <0
with the slope 0... | 0405049v1 |
2004-05-07 | Partial Covering Interpretation of the X-Ray Spectrum of the NLS1 1H 0707-495 | The X-ray spectrum of 1H 0707-495 obtained with XMM-Newton showing a deep
flux drop at ~7 keV (Boller et al. 2002) is studied based on the partial
covering concept. The previously inferred extreme iron overabundance can be
reduced down to ~3x solar if the hard component gradually steepens at high
energies. The spectral... | 0405158v1 |
2004-05-13 | Outflows in Regions of Star Formation | The high spatial and spectral resolution offered by the new generation of
infrared spectrometers at ESO is optimally suited for the observational study
of outflows from young stellar objects. Models of interstellar shock waves
would benefit from observations of spectrally resolved line profiles. This
applies also to at... | 0405248v1 |
2004-05-13 | Isothermal Shock Formation in Non-Equatorial Accretion Flows around Kerr Black Holes | We explore isothermal shock formation in non-equatorial, adiabatic accretion
flows onto a rotating black hole, with possible application to some active
galactic nuclei (AGNs). The isothermal shock jump conditions as well as the
regularity condition, previously developed for one-dimensional (1D) flows in
the equatorial ... | 0405269v1 |
2004-05-26 | Nucleosynthesis inside Gamma-Ray Burst Accretion Disks | We investigate nucleosynthesis inside both a gamma-ray burst accretion disk
and a wind launched from an inner region of the disk using one-dimensional
models of the disk and wind and a nuclear reaction network. Far from a central
black hole, the composition of accreting gas is taken to be that of an O-rich
layer of a m... | 0405510v1 |
2004-05-28 | Stars as thermonuclear reactors: their fuels and ashes | Atomic nuclei are transformed into each other in the cosmos by nuclear
reactions inside stars: -- the process of nucleosynthesis. The basic concepts
of determining nuclear reaction rates inside stars and how they manage to burn
their fuel so slowly most of the time are discussed. Thermonuclear reactions
involving proto... | 0405568v1 |
2004-06-05 | Fe II and Mg II in Luminous, Intermediate-Redshift Narrow-line Seyfert 1 Galaxies from the Sloan Digital Sky Survey | We present results from analysis of spectra from a sample of ~900 quasars
from the Sloan Digital Sky Survey. These objects were selected for their
intermediate redshift (1.2<z<1.8), placing MgII and UV FeII in the optical band
pass, relatively narrow MgII lines, and moderately good signal-to-noise-ratio
spectra. Using ... | 0406137v2 |
2004-06-09 | An Observation of the Intermediate Polar XY Arietis with Chandra | Chandra serendipitously observed the eclipsing (80 deg < i < 84 deg)
intermediate polar, XY Arietis (=H0253+193), in two separate but continuous
observations five weeks apart. XY Ari was in a quiescent state during both
observations. We pursue the study of phase-resolved spectra for this system
focusing on the Fe K lin... | 0406245v1 |
2004-06-29 | A New Contributor to Chemical Evolution in High-Redshift Galaxies | The recent discovery of a new population of stars exhibiting unusual
elemental abundance patterns characterized by enhanced Ti to Ga elements and
low alpha and n-capture elements suggests the contribution of a new class of
supernovae, probably a kind of Type Ia supernovae associated with close binary
evolution. The rol... | 0406636v1 |
2004-07-03 | Beyond the iron group: heavy metals in hot subdwarfs | We report the discovery of strong photospheric resonance lines of Ga III, Ge
IV, Sn IV and Pb IV in the UV spectra of more than two dozen sdB and sdOB stars
at temperatures ranging from 22000 K to 40000 K. Lines of other heavy elements
are also detected, however in these cases more atomic data are needed. Based on
thes... | 0407067v1 |
2004-07-07 | A possible feature of thermal matter in relativistic jets of radio-loud quasars | It has been suggested that relativistic jets in quasars may contain a
considerable amount of thermal matter. In this paper, we explore the
possibility that the K-alpha line from the thermal matter may appear at tens of
keV due to a high Doppler blue-shift. In the jet comoving frame, the energy
density of photons origin... | 0407123v1 |
2004-07-08 | Optical and near infrared observations of SN 1998bu | Infrared and optical spectra of SN 1998bu at an age of one year after
explosion are presented. The data show evidence for the radioactive decay of
56Co to 56Fe, long assumed to be the powering source for the supernova light
curve past maximum light. The spectra provide direct evidence for at least 0.4
solar masses of i... | 0407177v1 |
2004-07-21 | X-ray binaries and their descendants: binary radio pulsars; evidence for three classes of neutron stars? | An important recent discovery by Pfahl et al. (2002) is that there are two
classes of Be X-ray binaries: one with orbits of small eccentricity (<0.25), in
which the neutron stars received hardly any kick velocity at birth and a class
with substantial orbital eccentricities, in which the neutron stars received a
kick ve... | 0407451v1 |
2004-07-23 | Neutrinos from microquasars | The jets of microquasars with high-mass stellar companions are exposed to the
dense matter field of the stellar wind as well as to the photon densities found
in the surrounding medium. Photopion and proton-proton interactions could then
lead to copious production of neutrinos. In this work, we analyze the hadronic
micr... | 0407494v1 |
2004-07-27 | The isolated elliptical NGC 4555 observed with Chandra | We present analysis of a Chandra observation of the elliptical galaxy NGC
4555. The galaxy lies in a very low density environment, either isolated from
all galaxies of similar mass or on the outskirts of a group. Despite this, NGC
4555 has a large gaseous halo, extending to ~60 kpc. We find the mean gas
temperature to ... | 0407552v1 |
2004-08-03 | The Influence of Reaction Rates on the Final p-Abundances | The astrophysical p-process is responsible for the origin of the proton rich
nuclei,which are heavier than iron. A huge network involving thousands of
reaction rates is necessary to calculate the final p-abundances. But not all
rates included in the network have a strong influence on the p-nuclei
abundances. The p-proc... | 0408060v1 |
2004-08-26 | The narrow-line quasar NAB 0205+024 observed with XMM-Newton | The XMM-Newton observation of the narrow-line quasar NAB 0205+024 reveals
three striking differences since it was last observed in the X-rays with ASCA.
Firstly, the 2-10 keV power-law is notably steeper. Secondly, a hard X-ray
flare is detected, very similar to that seen in I Zw 1. Thirdly, a strong and
broad emission... | 0408507v1 |
2004-09-13 | Flux and energy modulation of redshifted iron emission in NGC3516: implications for the black hole mass | We report the tentative detection of the modulation of a transient,
redshifted Fe Kalpha emission feature in the X-ray spectrum of the Seyfert
galaxy NGC3516. The detection of the spectral feature at 6.1 keV, in addition
to a stable 6.4 keV line, has been reported previously. We find on re-analysing
the XMM-Newton data... | 0409293v1 |
2004-09-14 | Cosmogenic Neutrinos from Ultra-High Energy Nuclei | We calculate the flux of neutrinos generated by the propagation of ultra-high
energy iron over cosmological distances and show that even if ultra-high energy
cosmic rays are composed of heavy nuclei, a significant flux of high-energy
neutrinos should be present throughout the universe. The resulting neutrino
flux has a... | 0409316v2 |
2004-09-22 | Thorium-rich halo star HD221170: further evidence against the universality of the r-process | We report the abundance determination in the atmosphere of the bright halo
star HD221170. The spectra were taken with the Terskol Observatory's 2.0-m
telescope with a resolution R=45000 and signal-to-noise ratio up to 250 in the
wavelength region 3638-10275 \AA. The adopted atmospheric parameters correspond
to an effec... | 0409547v1 |
2004-09-24 | Three-Dimensional Delayed-Detonation Model of Type Ia Supernova | We study a Type Ia supernova explosion using large-scale three-dimensional
numerical simulations based on reactive fluid dynamics with a simplified
mechanism for nuclear reactions and energy release. The initial deflagration
stage of the explosion involves a subsonic turbulent thermonuclear flame
propagating in the gra... | 0409598v1 |
2004-09-26 | The Low X-Ray State of LS 5039 / RX J1826.2-1450 | Recent XMM-Newton and Chandra observations of the high mass X-ray binary LS
5039 / RX J1826.2-1450 caught the source in a faint X-ray state. In contrast
with previous RXTE observations, we fail to detect any evidence of iron line
emission. We also fail to detect X-ray pulsations. The X-ray spectrum can be
well fitted b... | 0409608v1 |
2004-09-27 | A puzzling event during the X-ray emission of the binary system GX 1+4 | We report on a long X-ray observation of the slow-rotating binary pulsar GX
1+4. BeppoSAX observed, in the 0.1-200 keV energy range, an event in which the
source flux dropped for almost a day, and then recovered. During this event
only the high-energy emission was found to be pulsed and the pulsations were
shifted in p... | 0409626v3 |
2004-09-29 | Fluorescence photons produced in air by extensive air showers | The air fluorescence technique has long been used to detect extensive air
showers and to reconstruct its geometry and energy. The fluorescence photon
yield of an electron in air is of main importance in the reconstruction
procedure. Historically, the fluorescence yield used in the reconstruction of
the showers is appro... | 0409727v1 |
2004-10-05 | Black Hole Spin in AGN and GBHCs | We discuss constraints on black hole spin and spin-related astrophysics as
derived from X-ray spectroscopy. After a brief discussion about the robustness
with which X-ray spectroscopy can be used to probe strong gravity, we summarize
how these techniques can constrain black hole spin. In particular, we highlight
XMM-Ne... | 0410116v1 |
2004-10-08 | Magnetorotational supernovae | We present the results of 2D simulations of the magnetorotational model of a
supernova explosion. After the core collapse the core consists of rapidly a
rotating proto-neutron star and a differentially rotating envelope. The
toroidal part of the magnetic energy generated by the differential rotation
grows linearly with... | 0410234v2 |
2004-10-19 | Metallicity measurements using atomic lines in M and K dwarf stars | We report the first survey of chemical abundances in M and K dwarf stars
using atomic absorption lines in high resolution spectra. We have measured Fe
and Ti abundances in 35 M and K dwarf stars using equivalent widths measured
from (lambda / Delta lambda) = 33,000 spectra. Our analysis takes advantage of
recent improv... | 0410452v1 |
2004-10-22 | Is the interstellar gas of starburst galaxies well mixed? | The extent to which the ISM in galaxies is well mixed is not yet settled.
Measured metal abundances in the diffuse neutral gas of star--forming gas--rich
dwarf galaxies are deficient with respect to that of the ionized gas. The
reasons, if real, are not clear and need to be based on firm grounds. Far-UV
spectroscopy of... | 0410528v1 |
2004-10-29 | On the primary particle type of the most energetic Fly's Eye event | The longitudinal profile of the 320 EeV event observed by the Fly's Eye
experiment is analysed. A method of testing the hypothesis of a specific
primary particle type is described. Results for different particle types are
summarized. For hadronic primaries between proton and iron nuclei, the
discrepancy between observe... | 0410739v1 |
2004-11-08 | The Metallicity dependence of the Cepheid Period-Luminosity relation: methodology and results | We present the results of an observational campaign undertaken to assess the
influence of the iron content on the Cepheid Period-Luminosity relation. Our
data indicate that this dependence is not well represented by a simple linear
relation. Rather, the behaviour is markedly non monotonic, with the correction
peaking a... | 0411190v1 |
2004-11-10 | High Resolution Spectroscopy of 4U 1728-34 from a Simultaneous Chandra-RXTE Observation | We report on a simultaneous Chandra and RossiXTE observation of the LMXB
atoll bursting source 4U 1728-34 performed on 2002 March 3-5. We fitted the
1.2-35 keV continuum spectrum with a blackbody plus a Comptonized component. An
overabundance of Si by a factor of ~2 with respect to Solar abundance is
required for a sat... | 0411270v2 |
2004-11-15 | XMM-Newton observations of the Lockman Hole: III. A relativistic Fe line in the mean X-ray spectra of type-1 and type-2 AGN | Using the 770 ksec XMM-Newton survey of the Lockman Hole field in combination
with extensive optical identifications of the AGN population, we derive an
average rest-frame spectrum of AGN types-1 and 2. The most prominent feature in
the averaged spectrum is a strong fluorescent Fe line. In both type-1 and
type-2 AGN, a... | 0411340v2 |
2004-11-25 | Muons with E_th >= 1 Gev and Mass Composition in the Energy Range 10^{18}-10^{20} ev Observed by Yakutsk Eas Array | The ratio of the muon flux density to charged particle flux density at
distances of 300 and 600 m from the shower axis ($\rhom(300)/\rhos(300)$ and
$\rhom(600)/\rhos(600)$) is measured. In addition, the energy dependence of
$\rhom(1000)$ is analysed for showers with energies above $10^{18}$ eV. A
comparison between the... | 0411683v2 |
2004-12-03 | Stellar Evolution with Enriched Surface Convection Zones I. General Effects of Planet Consumption | Abundance analyses of stars with planets have revealed that their
metallicities are enhanced relative to field stars. Such a trend was originally
suggested to be due to accretion of iron-rich planetary material. Based on this
assumption, we have developed a stellar evolution code to model stars with
non-uniform metalli... | 0412104v2 |
2004-12-09 | XMM-Newton observation of 4U 1543-475: the X-ray spectrum of a stellar-mass black-hole at low luminosity | We report the results of an observation of the galactic black-hole binary 4U
1543-475 performed by XMM-Newton on 2002 August 18, about two months after the
start of an outburst detected by Rossi-XTE. Despite the relatively low flux of
the source, corresponding to a luminosity Lx ~ 4x10^34 erg/s (i.e. about
10^(-5) time... | 0412209v1 |
2004-12-15 | The XMM-Newton spectrum of the high-z optically-obscured QSO RX J1343.4+0001: a classic radio quiet QSO | We present a 30 ks XMM-Newton observation of the z = 2.35 Type II radio quiet
quasar RX J1343.4+0001. These data provide the first good quality X-ray
spectrum for this object. We measured a continuum slope Gamma = 1.85+/-0.10
with only an upper limit on the column density of the absorbing material of
Nh(z) <~ 10^22 cm^... | 0412360v1 |
2004-12-15 | Determining the grain composition of the interstellar medium with high resolution X-ray spectroscopy | We investigate the ability of high resolution X-ray spectroscopy to directly
probe the grain composition of the interstellar medium. Using iron K-edge
experimental data of likely ISM dust candidates taken at the National
Synchrotron Light Source at Brookhaven National Laboratory and the Advanced
Photon Source at Argonn... | 0412393v1 |
2004-12-16 | The Metallicity of Post-T Tauri Stars: A preliminary approach to the understanding of the metal enrichment of stars harboring planets | The metallicity of young low mass Post-T Tauri stars in coeval associations
is practically unknown. This work is the beginning of a systematic measurement
of these metallicities based on high resolution spectra of low rotating members
of these associations. Here, we present an application by examining the
behavior of t... | 0412398v1 |
2004-12-19 | Extreme Test of Quantum Theory with Black Holes | We propose an extreme test of quantum theory using astrophysical black holes
and entangled photons from atomic cascades. The identification of a cascade
emission close to a black-hole event horizon would allow us to observe photons
entangled with partners that have fallen behind the horizon. The experiment
involves tes... | 0412503v1 |
2005-01-20 | Superfluidity in the Solar Interior: Implications for Solar Eruptions and Climate | Efforts to understand unusual weather or abrupt changes in climate have been
plagued by deficiencies of the standard solar model (SSM). While it assumes
that our primary source of energy began as a homogeneous ball of hydrogen (H)
with a steady, well-behaved H-fusion reactor at its core, observations instead
reveal a v... | 0501441v1 |
2005-01-31 | New Elemental Abundances for V1974 Cygni | We present a new analysis of existing optical and ultraviolet spectra of the
ONeMg nova V1974 Cygni 1992. Using these data and the photoionization code
Cloudy, we have determined the physical parameters and elemental abundances for
this nova. Many of the previous studies of this nova have made use of incorrect
analyses... | 0501648v1 |
2005-02-28 | Nuclear Astrophysics | Nuclear physics has a long and productive history of application to
astrophysics which continues today. Advances in the accuracy and breadth of
astrophysical data and theory drive the need for better experimental and
theoretical understanding of the underlying nuclear physics. This paper will
review some of the scenari... | 0502588v1 |
2005-03-08 | One-armed Spiral Instability in a Low T/|W| Postbounce Supernova Core | A three-dimensional, Newtonian hydrodynamic technique is used to follow the
postbounce phase of a stellar core collapse event. For realistic initial data
we have employed post core-bounce snapshots of the iron core of a 20 solar mass
star. The models exhibit strong differential rotation but have centrally
condensed den... | 0503187v2 |
2005-03-23 | Abundance trends in kinematical groups of the Milky Way's disk | We have compiled a large catalogue of metallicities and abundance ratios from
the literature in order to investigate abundance trends of several alpha and
iron peak elements in the thin disk and the thick disk of the Galaxy. The
catalogue includes 743 stars with abundances of Fe, O, Mg, Ca, Ti, Si, Na, Ni
and Al in the... | 0503498v1 |
2005-03-30 | X-ray line tomography of AGN-induced motion in clusters of galaxies | The thermal broadening of emission lines of heavy ions is small enough such
that Doppler shifts due to bulk motions may be detected with the next
generation of X-ray observatories. This opens up the possibility to study gas
velocities in the intra-cluster medium. Here we study the effect of bulk
motions induced by a ce... | 0503656v2 |
2005-03-30 | On the fine structure of the sunspot penumbrae. II. The nature of the Evershed flow | We investigate the fine structure of the sunspot penumbra by means of a model
that allows for a flux tube in horizontal pressure balance with the magnetic
background atmosphere in which it is embedded. We apply this model to
spectropolarimetric observations of two neutral iron lines at 1.56 $\mu$m and
invert several ra... | 0503677v1 |
2005-04-12 | The temperature structure in the core of Sersic 159-03 | We present results from a new 120 ks XMM-Newton observation of the cluster of
galaxies Sersic 159-03. In this paper we focus on the high-resolution X-ray
spectra obtained with the Reflection Grating Spectrometer (RGS). The spectra
allow us to constrain the temperature structure in the core of the cluster and
determine ... | 0504262v1 |
2005-05-06 | Dust Scattering in Miras R Car and RR Sco resolved by optical interferometric polarimetry | We present optical interferometric polarimetry measurements of the Mira-like
variables R Car and RR Sco, using the Sydney University Stellar Interferometer.
By making visibility measurements in two perpendicular polarisations, the
relatively low-surface brightness light scattered by atmospheric dust could be
spatially ... | 0505112v1 |
2005-05-14 | Family ties: abundances in Terzan 7, a Sgr dSph globular cluster | We study the chemical composition of 5 giant stars in the globular cluster
Terzan 7 associated with the Sagittarius dwarf spheroidal galaxy (Sgr dSph),
based on high resolution UVES-VLT spectra. We confirm the metallicity found by
previous high resolution investigations: [Fe/H] ~ -0.6. We also show that this
cluster di... | 0505307v1 |
2005-05-19 | Early star formation in the Galaxy from beryllium and oxygen abundances | We investigate the evolution of the star formation rate in the early Galaxy
using beryllium and oxygen abundances in metal poor stars. Specifically, we
show that stars belonging to two previously identified kinematical classes (the
so-called ``accretion'' and ``dissipative'' populations) are neatly separated
in the [O/... | 0505396v1 |
2005-06-20 | Nitrogen-deficient and iron-rich associated absorbers with oversolar metallicities towards the quasar HE0141-3932 | HE0141-3932 (zem=1.80) is a bright blue radio-quite quasar which reveals an
emission line spectrum with an unusually weak Ly-alpha line. In addition, large
redshift differences (Delta z=0.05) are observed between high ionization and
low ionization emission lines. Absorption systems identified at z=1.78, 1.71,
and 1.68 ... | 0506446v1 |
2005-06-24 | Kappa-mechanism excitation of retrograde mixed modes in rotating B-type stars | I examine the stability of retrograde mixed modes in rotating B-type stars.
These modes can be regarded as a hybrid between the Rossby modes that arise
from conservation of vorticity, and the Poincare modes that are gravity waves
modified by the Coriolis force. Using a non-adiabatic pulsation code based
around the trad... | 0506580v3 |
2005-06-25 | The Ital-FLAMES survey of the Sagittarius dwarf Spheroidal galaxy. I. Chemical abundances of bright RGB stars | We present iron and $\alpha$ element (Mg, Ca, Ti) abundances for a sample of
15 Red Giant Branch stars belonging to the main body of the Sagittarius dwarf
Spheroidal galaxy. Abundances have been obtained from spectra collected using
the high resolution spectrograph FLAMES-UVES mounted at the VLT. Stars of our
sample ha... | 0506622v2 |
2005-07-08 | The relativistic shift of narrow spectral features from black-hole accretion discs | Transient spectral features have been discovered in the X-ray spectra of
Active Galactic Nuclei, mostly in the 5--7 keV energy range. Several
interpretations were proposed for the origin of these features. We examined a
model of Doppler boosted blue horns of the iron line originating from a spot in
a black hole accreti... | 0507196v1 |
2005-07-08 | Probing the outer edge of an accretion disk: A Her X-1 turn-on observed with RXTE | We present the analysis of Rossi X-ray Timing Explorer (RXTE) observations of
the turn-on phase of a 35 day cycle of the X-ray binary Her X-1. During the
early phases of the turn-on, the energy spectrum is composed of X-rays
scattered into the line of sight plus heavily absorbed X-rays. The energy
spectra in the 3-17 k... | 0507198v1 |
2005-07-14 | Heavy element abundances in DAO white dwarfs measured from FUSE data | We present heavy element abundance measurements for 16 DAO white dwarfs,
determined from Far-Ultraviolet Spectroscopic Explorer {FUSE} spectra. Evidence
of absorption by heavy elements was found in the spectra of all the objects.
Measurements were made using models that adopted the temperatures, gravities
and helium ab... | 0507341v1 |
2005-07-19 | The Type Ia Supernova Rate | We explore the idea that the Type Ia supernovae (SNe Ia) rate consists of two
components: a prompt piece that is proportional to the star formation rate
(SFR) and an extended piece that is proportional to the total stellar mass. We
fit the parameters of this model to the local observations of Mannucci and
collaborators... | 0507456v2 |
2005-07-20 | UHECR Composition Measurements Using the HiRes-II Detector | While stereo measurements of extensive air showers allow a more precise
determination of the depth of shower maximum and hence the composition of
UHECR's, monocular measurements allow one to go much lower in energy. Since the
composition of UHECR seems to constant throughout the HiRes stereo energy range
but changing j... | 0507483v1 |
2005-07-27 | Gamma-Rays from Single Lobe Supernova Explosions | Multi-dimensional simulations of the neutrino-driven mechanism behind
core-collapse supernovae have long shown that the explosions from this
mechanism would be asymmetric. Recently, detailed core-collapse simulations
have shown that the explosion may be strongest in a single direction. We
present a suite of simulations... | 0507651v1 |
2005-08-10 | Relativistic outflow in CXO CDFS J033260.0-274748 | In this letter we report the detection of a strong and extremely blueshifted
X-ray absorption feature in the 1 Ms Chandra spectrum of CXO CDFS
J033260.0-274748, a quasar at z = 2.579 with L_2-10keV ~ 4x10^44 ergs/s. The
broad absorption feature at ~ 6.3 keV in the observed frame can be fitted
either as an absorption ed... | 0508225v1 |
2005-08-19 | The magnetic structure of neutron stars and their surface-to-core temperature relation | We study the relation between the mean effective surface temperature T_s and
the internal temperature T_b for magnetic neutron stars, assuming that the
magnetic field near the surface has a presumably small-scale structure. The
heavy-element (iron) and light-element (accreted) heat-blanketing envelopes are
considered, ... | 0508415v2 |
2005-08-29 | Highly ionized iron absorption lines from outflowing gas in the X-ray spectrum of NGC 1365 | We present the discovery of four absorption lines in the X-ray spectrum of
the Seyfert Galaxy NGC 1365, at energies between 6.7 and 8.3 keV. The lines are
detected with high statistical confidence (from >20sigma for the strongest to
\~4sigma for the weakest) in two XMM-Newton observations 60 ksec long. We also
detect t... | 0508608v1 |
2005-09-07 | An Observationally Motivated Framework for AGN Heating of Cluster Cores | The cooling-flow problem is a long-standing puzzle that has received
considerable recent attention, in part because the mechanism that quenches
cooling flows in galaxy clusters is likely to be the same mechanism that
sharply truncates the high end of the galaxy luminosity function. Most of the
recent models for halting... | 0509176v1 |
2005-09-09 | A Comparison of the Chemical Evolutionary Histories of the Galactic Thin Disk and Thick Disk Stellar Populations | We have studied 23 long-lived G dwarfs that belong to the thin disk and thick
disk stellar populations. Abundances have been derived for 24 elements: O, Na,
Mg, Al, Si, Ca, Ti, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Ba, La, Ce,
Nd, and Eu. We find that the behavior of [alpha/Fe] and [Eu/Fe] vs. [Fe/H] are
quite ... | 0509267v1 |
2005-09-13 | Formation of the First Stars | How and when did the first generation of stars form at the end of the cosmic
dark ages? Quite generically, within variants of the cold dark matter model of
cosmological structure formation, the first sources of light are expected to
form in ~ 10^{6} M_sun dark matter potential wells at redshifts z > 20. I
discuss the p... | 0509354v1 |
2005-09-15 | Evolution of Galaxies and the Tully-Fisher Relation | We study the evolution of the [O/Fe]-[Fe/H] relation and the dependence of
the iron abundance on distance from the galactic plane z in a one-zone model
for a disk galaxy, starting from the beginning of star formation (Wiebe98). We
obtain good agreement with the observational data, including, for the first
time, agreeme... | 0509423v2 |
2005-09-16 | Analysis of extensive air showers with the hybrid code SENECA | The ultrahigh energy tail of the cosmic ray spectrum has been explored with
unprecedented detail. For this reason, new experiments are exerting a severe
pressure on extensive air shower modeling. Detailed fast codes are in need in
order to extract and understand the richness of information now available. In
this sense ... | 0509503v1 |
2005-09-20 | Acceptance of fluorescence detectors and its implication in energy spectrum inference at the highest energies | Along the years HiRes and AGASA experiments have explored the fluorescence
and the ground array experimental techniques to measure extensive air showers,
being both essential to investigate the ultra-high energy cosmic rays. However,
such Collaborations have published contradictory energy spectra for energies
above the... | 0509597v1 |
2005-09-28 | An abundance analysis of the symbiotic star CH Cyg | The photospheric abundances for the cool component of the symbiotic star CH
Cyg were calculated for the first time using high-resolution near-infrared
spectra and the method of of standard LTE analysis and atmospheric models. The
iron abundance for CH Cyg was found to be solar, [Fe/H] = 0.0+/-0.19. The
atmospheric para... | 0509852v1 |
2005-10-07 | Dust obscuration of DLA galaxies | We show that the extinction of quasar absorbers increases exponentially with
the logarithmic column density of any volatile metal (e.g. zinc), with a
charateristic turning point above which the quasars are severely dimmed. We
derive the relation between extinction, HI column density, metallicity and
fraction of iron in... | 0510216v1 |
2005-10-14 | Thermonuclear supernova simulations with stochastic ignition | We apply an ad hoc model for dynamical ignition in three-dimensional
numerical simulations of thermonuclear supernovae assuming pure deflagrations.
The model makes use of the statistical description of temperature fluctuations
in the pre-supernova core proposed by Wunsch & Woosley (2004). Randomness in
time is implemen... | 0510427v1 |
2005-10-18 | The Chemical Composition of Cepheids in the Milky Way and the Magellanic Clouds | We have measured the elemental abundances of 68 Galactic and Magellanic
Cepheids from FEROS and UVES high-resolution and high signal-to-noise spectra
in order to establish the influence of the chemical composition on the
properties of these stars (see Romaniello et al. 2005). Here we describe the
robust analytical proc... | 0510514v1 |
2005-10-19 | On the fine structure of the sunspot penumbrae. III The vertical extension of penumbral filaments | In this paper we study the fine structure of the penumbra as inferred from
the uncombed model (flux tube embedded in a magnetic surrounding) when applied
to penumbral spectropolarimetric data from the neutral iron lines at 6300 \AA.
The inversion infers very similar radial dependences in the physical quantities
(LOS ve... | 0510586v1 |
2005-10-27 | Phase-resolved spectroscopy of the helium dwarf nova 'SN 2003aw' in quiescence | High time resolution spectroscopic observations of the ultra-compact helium
dwarf nova 'SN 2003aw' in its quiescent state at V=20.5 reveal its orbital
period at 2027.8 +/- 0.5 seconds or 33.80 minutes. Together with the
photometric 'superhump' period of 2041.5 +/- 0.5 seconds, this implies a mass
ratio q of 0.036. We c... | 0510767v1 |
2005-11-17 | X-ray reflections on AGN | X-ray reflection generates much of the spectral complexity in the X-ray
spectra of AGN. It is argued that strong relativistic blurring of the
reflection spectrum should commonly be expected from objects accreting at a
high Eddington rate. The good agreement found between the local density in
massive black holes and the... | 0511537v1 |
2005-12-15 | The mass of cosmic rays above 1017 eV | Interpretation of the energy spectrum and arrival distribution of cosmic rays
is complicated by lack of knowledge of the nature of the primaries. We review
claims for the mass composition above 1017 eV where it can be determined only
indirectly from air-shower observables. Difficulties in comparisons between
data arise... | 0512408v1 |
2005-12-16 | Lateral distribution of Cherenkov light in extensive air showers at high mountain altitude produced by different primary particles in wide energy range | The general aim of this work is to obtain the lateral distribution of
atmospheric Cherenkov light in extensive air showers produced by different
primary particles precisely by. protons, Helium, Iron, Oxygen, Carbon,
Nitrogen, Calcium, Silicon and gamma quanta in wide energy range at high
mountain observation level of C... | 0512432v1 |
2005-12-16 | INTEGRAL and RXTE Observations of Centaurus A | INTEGRAL and RXTE performed three simultaneous observations of the nearby
radio galaxy Cen A in 2003 March, 2004 January, and 2004 February with the
goals of investigating the geometry and emission processes via the
spectral/temporal variability of the X-ray/low energy gamma ray flux, and
intercalibration of the INTEGR... | 0512451v1 |
2005-12-20 | An Overview of Extremely Large Telescopes Projects | IAU Symposium 232 allows a snapshot of ELTs at a stage when design work in
several critical mass projects has been seriously underway for two to three
years. The status and som eof the main initial design choices are reviewed for
the North American Giant Magellan Telescope (GMT) and the Thirty Meter
Telescope (TMT) pro... | 0512499v1 |
2005-12-21 | The Oxygen Abundance of HE 1327-2326 | From a newly obtained VLT/UVES spectrum we have determined the oxygen
abundance of HE 1327-2326, the most iron-poor star known to date. UV-OH lines
yield a 1D LTE abundance of [O/Fe]_OH = 3.7 (subgiant case) and [O/Fe]_OH = 3.4
(dwarf case). Using a correction of -1.0 dex to account for 3D effects on OH
line formation,... | 0512543v1 |
2006-01-08 | Excitation of g modes in Wolf-Rayet stars by a deep opacity bump | We examine the stability of l=1 and l=2 g modes in a pair of nitrogen-rich
Wolf-Rayet stellar models characterized by differing hydrogen abundances. We
find that modes with intermediate radial orders are destabilized by a kappa
mechanism operating on an opacity bump at an envelope temperature log T ~ 6.25.
This `deep o... | 0601154v2 |
2006-01-18 | Observable Effects of Dust Formation in Dynamic Atmospheres of M-type Mira Variables | The formation of dust with temperature-dependent non-grey opacity is
considered in a series of self-consistent model atmospheres at different phases
of an O-rich Mira variable of mass 1.2 $M_\odot$. Photometric and
interferometric properties of these models are predicted under different
physical assumptions regarding t... | 0601383v1 |
2006-02-21 | Tracing gas motions in the Centaurus Cluster | We apply the stochastic model of iron transport developed by Rebusco et. al.
(2005) to the Centaurus cluster. Using this model, we find that an effective
diffusion coefficient D in the range 2x10^28 - 4x10^28 cm^2 s^-1 can
approximately reproduce the observed abundance distribution. Reproducing the
flat central profile... | 0602466v1 |
2006-02-25 | Luminosity dependent study of the High Mass X-ray Binary Pulsar 4U~0114+65 with ASCA | Here we report the spectral characteristics of the high and low states of the
pulsar 4U~0114+65 and examine the change in the parameters of the spectral
model. A power law and a photoelectric absorption by material along the line of
sight together with a high energy cut-off suffice to describe the continuum
spectrum in... | 0602558v1 |
2006-03-03 | Metallicity structure in X-ray bright galaxy groups | Using Chandra X-ray data of a sample of 15 X-ray bright galaxy groups, we
present preliminary results of a coherent study of the radial distribution of
metal abundances in the hot gas in groups. The iron content in group outskirts
is found to be lower than in clusters by a factor of ~2, despite showing mean
levels in t... | 0603085v1 |
2006-03-16 | Yields of Population III Supernovae and the Abundance Patterns of Extremely Metal-Poor Stars | The abundance patterns of extremely metal-poor (EMP) stars provide us with
important information on nucleosynthesis in supernovae (SNe) formed in a Pop
III or EMP environment, and thus on the nature of the first stars in the
Universe. We review nucleosynthesis yields of various types of those SNe,
focusing on core-coll... | 0603433v1 |
2006-04-01 | Chemical abundances in LMC stellar populations I. The Inner disk sample Based on observations collected at the VLT UT2 telescope | The advent of the new class 8 meters telescopes allows for the first time the
detailed study of numerous stars of galaxies other than our own. The Large
Magellanic Cloud is one of the most interesting targets due to its proximity
and its relatively face-on disk, permitting to separate populations pertaining
to the diff... | 0604009v2 |
2006-04-03 | Abundance analysis of cool extreme helium star: LSS 3378 | Abundance analysis of the cool extreme helium (EHe) star LSS 3378 is
presented. The abundance analysis is done using LTE line formation and LTE
model atmospheres constructed for EHe stars.
The atmosphere of LSS 3378 shows evidence of H-burning, He-burning, and
s-process nucleosynthesis. The derived abundances of iron... | 0604023v1 |
2006-04-03 | High resolution infrared spectroscopy of the old open cluster NGC6791 | We report abundance analysis for 6 M giant members of the old open cluster
NGC6791, based on infrared spectroscopy (1.5-1.8 micron) at R=25,000, using the
NIRSPEC spectrograph at the Keck II telescope. We find the iron abundance
<[Fe/H]>= +0.35 +/- 0.02$, confirming the super solar metallicity of this
cluster derived f... | 0604030v1 |
2006-04-13 | The flow field in the sunspot canopy | We investigate the flow field in the sunspot canopy using simultaneous Stokes
vector spectropolarimetry of three sunspots ($\theta$ = 27, 50, 75 deg) and
their surroundings in visible (630.15 and 630.25 nm) and near infrared (1564.8
and 1565.2 nm) neutral iron lines.} {To calibrate the Doppler shifts, we
compare an abs... | 0604301v1 |
2006-04-27 | Resonance scattering, absorption and off-centre abundance peaks in clusters of galaxies | A possible explanation for the central abundance dips found from
spatially-resolved X-ray spectroscopy of several groups and clusters of
galaxies is resonance scattering. A number of the prominent iron emission lines
are resonance lines. We construct a unique spectral model which takes account
of resonance scattering f... | 0604575v1 |
2006-05-04 | Variable iron-line emission near the black hole of Markarian 766 | We investigate the link between ionised Fe X-ray line emission and continuum
emission in the bright nearby AGN, Mrk 766. A new long (433 ks) XMM-Newton
observation is analysed, together with archival data from 2000 and 2001. The
contribution from ionised line emission is measured and its time variations on
short (5-20 ... | 0605130v1 |
2006-06-13 | Unveiling the nature of the highly absorbed X-ray source SAXJ1748.2-2808 with XMM-Newton | We report on the results of an EPIC XMM-Newton observation of the faint
source SAXJ1748.2-2808 and the surrounding field. This source was discovered
during the BeppoSAX Galactic center survey performed in 1997-1998. A spatial
analysis resulted in the detection of 31 sources within the EPIC field of view.
SAXJ1748.2-280... | 0606307v1 |
2006-06-27 | Outgassing of Ordinary Chondritic Material and Some of its Implications for the Chemistry of Asteroids, Planets, and Satellites | We used chemical equilibrium calculations to model thermal outgassing of
ordinary chondritic material as a function of temperature, pressure, and bulk
compositions and use our results to discuss outgassing on asteroids and the
early Earth. The calculations include ~1,000 solids and gases of the elements
Al, C, Ca, Cl, ... | 0606671v1 |
2006-06-27 | They Came From the Deep in the Supernova: The Origin of TiC and Metal Subgrains in Presolar Graphite Grains | A new formation scenario for TiC and Fe,Ni-metal inclusions in presolar
graphite grains of supernova origin is described. The mineralogy and chemistry
require condensation of (Fe,Ni)-titanides from Fe, Ni, and Ti-rich gaseous
ejecta, subsequent carburization to make TiC and metal, and encapsulation into
graphite. Titan... | 0606673v1 |
2006-07-03 | Sulphur abundances in disk stars as determined from the forbidden 10821 A [SI] line | Aims: In this paper we aim to study the chemical evolution of sulphur in the
galactic disk, using a new optimal abundance indicator: the [SI] line at 10821
A. Similar to the optimal oxygen indicators, the [OI] lines, the [SI] line has
the virtues of being less sensitive to the assumed temperatures of the stars
investig... | 0607017v1 |
2006-07-06 | Enrichment in the Centaurus cluster of galaxies | We perform a detailed spatially-resolved, spectroscopic, analysis of the core
of the Centaurus cluster of galaxies using a deep Chandra X-ray observation and
XMM-Newton data. The Centaurus cluster core has particularly high metallicity,
upto twice Solar values, and we measure the abundances of Fe, O, Ne, Mg, Si, S,
Ar,... | 0607113v1 |
2006-07-11 | Atomic and Molecular Opacities for Brown Dwarf and Giant Planet Atmospheres | We present a comprehensive description of the theory and practice of opacity
calculations from the infrared to the ultraviolet needed to generate models of
the atmospheres of brown dwarfs and extrasolar giant planets. Methods for using
existing line lists and spectroscopic databases in disparate formats are
presented a... | 0607211v4 |
2006-07-13 | The puzzling abundance pattern of HD134439 and HD134440 | Abundances of 18 elements are determined for the common proper-motion pair,
HD134439 and HD134440, which shows high [Mn/Fe] and low [\alpha/Fe] ratios as
compared to normal halo stars. Moreover, puzzling abundances are indicated from
elements whose origins are normally considered to be from the same
nucleosynthesis his... | 0607287v1 |
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